Src homology 2 (SH2) domain found in the Src family of non-receptor tyrosine kinases; The Src family kinases are nonreceptor tyrosine kinases that have been implicated in pathways regulating proliferation, angiogenesis, invasion and metastasis, and bone metabolism. It is thought that transforming ability of Src is linked to its ability to activate key signaling molecules in these pathways, rather than through direct activity. As such blocking Src activation has been a target for drug companies. Src family members can be divided into 3 groups based on their expression pattern: 1) Src, Fyn, and Yes; 2) Blk, Fgr, Hck, Lck, and Lyn; and 3) Frk-related kinases Frk/Rak and Iyk/Bsk Of these, cellular c-Src is the best studied and most frequently implicated in oncogenesis. The c-Src contains five distinct regions: a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Src exists in both active and inactive conformations. Negative regulation occurs through phosphorylation of Tyr, resulting in an intramolecular association between phosphorylated Tyr and the SH2 domain of SRC, which locks the protein in a closed conformation. Further stabilization of the inactive state occurs through interactions between the SH3 domain and a proline-rich stretch of residues within the kinase domain. Conversely, dephosphorylation of Tyr allows SRC to assume an open conformation. Full activity requires additional autophosphorylation of a Tyr residue within the catalytic domain. Loss of the negative-regulatory C-terminal segment has been shown to result in increased activity and transforming potential. Phosphorylation of the C-terminal Tyr residue by C-terminal Src kinase (Csk) and Csk homology kinase results in increased intramolecular interactions and consequent Src inactivation. Specific phosphatases, protein tyrosine phosphatase a (PTPa) and the SH-containing phosphatases SHP1/SHP2, have also been shown to take a part in Src activation. Src is also activated by direct binding of focal adhesion kinase (Fak) and Crk-associated substrate (Cas) to the SH2 domain. SRC activity can also be regulated by numerous receptor tyrosine kinases (RTKs), such as Her2, epidermal growth factor receptor (EGFR), fibroblast growth factor receptor, platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR). In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd09933     1 EAEEWFFGKIKRKDAEKLLLAPGNPRGTFLIRESETTPGAYSLSVRDGDDARGDTVKHYRIRKLDNGGYYITTRATFPTL 80

                          90       100
                  ....*....|....*....|
gi 1907162151 232 QKLVKHYTEHADGLCHKLTT 251
Cdd:cd09933    81 QELVQHYSKDADGLCCRLTV 100

Src homology 3 domain of Yes Protein Tyrosine Kinase; Yes (or c-Yes) is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. c-Yes kinase is the cellular homolog of the oncogenic protein (v-Yes) encoded by the Yamaguchi 73 and Esh sarcoma viruses. It displays functional overlap with other Src subfamily members, particularly Src. It also shows some unique functions such as binding to occludins, transmembrane proteins that regulate extracellular interactions in tight junctions. Yes also associates with a number of proteins in different cell types that Src does not interact with, like JAK2 and gp130 in pre-adipocytes, and Pyk2 in treated pulmonary vein endothelial cells. Although the biological function of Yes remains unclear, it appears to have a role in regulating cell-cell interactions and vesicle trafficking in polarized cells. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*...
gi 1907162151  92 TIFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKSGYIPSNYVVPAD 149
Cdd:cd12007     1 TIFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKNGYIPSNYVAPAD 58

Src homology 2 (SH2) domain found in the Src family of non-receptor tyrosine kinases; The Src family kinases are nonreceptor tyrosine kinases that have been implicated in pathways regulating proliferation, angiogenesis, invasion and metastasis, and bone metabolism. It is thought that transforming ability of Src is linked to its ability to activate key signaling molecules in these pathways, rather than through direct activity. As such blocking Src activation has been a target for drug companies. Src family members can be divided into 3 groups based on their expression pattern: 1) Src, Fyn, and Yes; 2) Blk, Fgr, Hck, Lck, and Lyn; and 3) Frk-related kinases Frk/Rak and Iyk/Bsk Of these, cellular c-Src is the best studied and most frequently implicated in oncogenesis. The c-Src contains five distinct regions: a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Src exists in both active and inactive conformations. Negative regulation occurs through phosphorylation of Tyr, resulting in an intramolecular association between phosphorylated Tyr and the SH2 domain of SRC, which locks the protein in a closed conformation. Further stabilization of the inactive state occurs through interactions between the SH3 domain and a proline-rich stretch of residues within the kinase domain. Conversely, dephosphorylation of Tyr allows SRC to assume an open conformation. Full activity requires additional autophosphorylation of a Tyr residue within the catalytic domain. Loss of the negative-regulatory C-terminal segment has been shown to result in increased activity and transforming potential. Phosphorylation of the C-terminal Tyr residue by C-terminal Src kinase (Csk) and Csk homology kinase results in increased intramolecular interactions and consequent Src inactivation. Specific phosphatases, protein tyrosine phosphatase a (PTPa) and the SH-containing phosphatases SHP1/SHP2, have also been shown to take a part in Src activation. Src is also activated by direct binding of focal adhesion kinase (Fak) and Crk-associated substrate (Cas) to the SH2 domain. SRC activity can also be regulated by numerous receptor tyrosine kinases (RTKs), such as Her2, epidermal growth factor receptor (EGFR), fibroblast growth factor receptor, platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR). In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd09933     1 EAEEWFFGKIKRKDAEKLLLAPGNPRGTFLIRESETTPGAYSLSVRDGDDARGDTVKHYRIRKLDNGGYYITTRATFPTL 80

                          90       100
                  ....*....|....*....|
gi 1907162151 232 QKLVKHYTEHADGLCHKLTT 251
Cdd:cd09933    81 QELVQHYSKDADGLCCRLTV 100

Src homology 3 domain of Yes Protein Tyrosine Kinase; Yes (or c-Yes) is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. c-Yes kinase is the cellular homolog of the oncogenic protein (v-Yes) encoded by the Yamaguchi 73 and Esh sarcoma viruses. It displays functional overlap with other Src subfamily members, particularly Src. It also shows some unique functions such as binding to occludins, transmembrane proteins that regulate extracellular interactions in tight junctions. Yes also associates with a number of proteins in different cell types that Src does not interact with, like JAK2 and gp130 in pre-adipocytes, and Pyk2 in treated pulmonary vein endothelial cells. Although the biological function of Yes remains unclear, it appears to have a role in regulating cell-cell interactions and vesicle trafficking in polarized cells. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*...
gi 1907162151  92 TIFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKSGYIPSNYVVPAD 149
Cdd:cd12007     1 TIFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKNGYIPSNYVAPAD 58

Src homology 2 domains; Src homology 2 domains bind phosphotyrosine-containing polypeptides via 2 surface pockets. Specificity is provided via interaction with residues that are distinct from the phosphotyrosine. Only a single occurrence of a SH2 domain has been found in S. cerevisiae.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151  154 EEWYFGKMGRKDAERLLLNPGNqrGIFLVRESETTKGAYSLSIRDwdevrGDNVKHYKIRKLDNGGYYITTRAQFDTLQK 233
Cdd:smart00252   1 QPWYHGFISREEAEKLLKNEGD--GDFLVRDSESSPGDYVLSVRV-----KGKVKHYRIRRNEDGKFYLEGGRKFPSLVE 73

                           90
                   ....*....|.
gi 1907162151  234 LVKHYTEHADG 244
Cdd:smart00252  74 LVEHYQKNSLG 84

Protein kinase; unclassified specificity; Phosphotransferases. The specificity of this class of kinases can not be predicted. Possible dual-specificity Ser/Thr/Tyr kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151  275 LRLEVKLGQGCFGEVWMGTWNGT-----TKVAIKTLKPGTMM--PEAFLQEAQIMKKLRHDKLVPLYAVVSE-EPIYIVT 346
Cdd:smart00221   1 LTLGKKLGEGAFGEVYKGTLKGKgdgkeVEVAVKTLKEDASEqqIEEFLREARIMRKLDHPNIVKLLGVCTEeEPLMIVM 80

                   ....*
gi 1907162151  347 EFMSK 351
Cdd:smart00221  81 EYMPG 85

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*...
gi 1907162151  95 VALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIaTGKSGYIPS 142
Cdd:pfam00018   1 VALYDYTAQEPDELSFKKGDIIIVLEKSEDGWWKGRNK-GGKEGLIPS 47

Src homology 2 (SH2) domain found in the Src family of non-receptor tyrosine kinases; The Src family kinases are nonreceptor tyrosine kinases that have been implicated in pathways regulating proliferation, angiogenesis, invasion and metastasis, and bone metabolism. It is thought that transforming ability of Src is linked to its ability to activate key signaling molecules in these pathways, rather than through direct activity. As such blocking Src activation has been a target for drug companies. Src family members can be divided into 3 groups based on their expression pattern: 1) Src, Fyn, and Yes; 2) Blk, Fgr, Hck, Lck, and Lyn; and 3) Frk-related kinases Frk/Rak and Iyk/Bsk Of these, cellular c-Src is the best studied and most frequently implicated in oncogenesis. The c-Src contains five distinct regions: a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Src exists in both active and inactive conformations. Negative regulation occurs through phosphorylation of Tyr, resulting in an intramolecular association between phosphorylated Tyr and the SH2 domain of SRC, which locks the protein in a closed conformation. Further stabilization of the inactive state occurs through interactions between the SH3 domain and a proline-rich stretch of residues within the kinase domain. Conversely, dephosphorylation of Tyr allows SRC to assume an open conformation. Full activity requires additional autophosphorylation of a Tyr residue within the catalytic domain. Loss of the negative-regulatory C-terminal segment has been shown to result in increased activity and transforming potential. Phosphorylation of the C-terminal Tyr residue by C-terminal Src kinase (Csk) and Csk homology kinase results in increased intramolecular interactions and consequent Src inactivation. Specific phosphatases, protein tyrosine phosphatase a (PTPa) and the SH-containing phosphatases SHP1/SHP2, have also been shown to take a part in Src activation. Src is also activated by direct binding of focal adhesion kinase (Fak) and Crk-associated substrate (Cas) to the SH2 domain. SRC activity can also be regulated by numerous receptor tyrosine kinases (RTKs), such as Her2, epidermal growth factor receptor (EGFR), fibroblast growth factor receptor, platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR). In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd09933     1 EAEEWFFGKIKRKDAEKLLLAPGNPRGTFLIRESETTPGAYSLSVRDGDDARGDTVKHYRIRKLDNGGYYITTRATFPTL 80

                          90       100
                  ....*....|....*....|
gi 1907162151 232 QKLVKHYTEHADGLCHKLTT 251
Cdd:cd09933    81 QELVQHYSKDADGLCCRLTV 100

Src homology 2 (SH2) domain found in Gardner-Rasheed feline sarcoma viral (v-fgr) oncogene homolog, Fgr; Fgr is a member of the Src non-receptor type tyrosine kinase family of proteins. The protein contains N-terminal sites for myristoylation and palmitoylation, a PTK domain, and SH2 and SH3 domains which are involved in mediating protein-protein interactions with phosphotyrosine-containing and proline-rich motifs, respectively. Fgr is expressed in B-cells and myeloid cells, localizes to plasma membrane ruffles, and functions as a negative regulator of cell migration and adhesion triggered by the beta-2 integrin signal transduction pathway. Multiple alternatively spliced variants, encoding the same protein, have been identified Fgr has been shown to interact with Wiskott-Aldrich syndrome protein. Fgr has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10367     1 QAEEWYFGKIGRKDAERQLLSPGNPRGAFLIRESETTKGAYSLSIRDWDQNRGDHVKHYKIRKLDTGGYYITTRAQFDTV 80

                          90
                  ....*....|....*....
gi 1907162151 232 QKLVKHYTEHADGLCHKLT 250
Cdd:cd10367    81 QELVQHYMEVNDGLCYLLT 99

Src homology 2 (SH2) domain found in Fyn; Fyn is a member of the Src non-receptor type tyrosine kinase family of proteins. Fyn is involved in the control of cell growth and is required in the following pathways: T and B cell receptor signaling, integrin-mediated signaling, growth factor and cytokine receptor signaling, platelet activation, ion channel function, cell adhesion, axon guidance, fertilization, entry into mitosis, and differentiation of natural killer cells, oligodendrocytes and keratinocytes. The protein associates with the p85 subunit of phosphatidylinositol 3-kinase and interacts with the Fyn-binding protein. Alternatively spliced transcript variants encoding distinct isoforms exist. Fyn is primarily localized to the cytoplasmic leaflet of the plasma membrane. Tyrosine phosphorylation of target proteins by Fyn serves to either regulate target protein activity, and/or to generate a binding site on the target protein that recruits other signaling molecules. FYN has been shown to interact with a number of proteins including: BCAR1, Cbl, Janus kinase, nephrin, Sky, tyrosine kinase, Wiskott-Aldrich syndrome protein, and Zap-70. Fyn has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10368     1 QAEEWYFGKLGRKDAERQLLSFGNPRGTFLIRESETTKGAYSLSIRDWDDMKGDHVKHYKIRKLDNGGYYITTRAQFETL 80

                          90       100
                  ....*....|....*....|.
gi 1907162151 232 QKLVKHYTEHADGLCHKLTTV 252
Cdd:cd10368    81 QQLVQHYSETANGLCKVLIVT 101

Src homology 2 (SH2) domain found in tyrosine kinase sarcoma (Src); Src is a member of the Src non-receptor type tyrosine kinase family of proteins. Src is thought to play a role in the regulation of embryonic development and cell growth. Members here include v-Src and c-Src. v-Src lacks the C-terminal inhibitory phosphorylation site and is therefore constitutively active as opposed to normal cellular src (c-Src) which is only activated under certain circumstances where it is required (e.g. growth factor signaling). v-Src is an oncogene whereas c-Src is a proto-oncogene. c-Src consists of three domains, an N-terminal SH3 domain, a central SH2 domain and a tyrosine kinase domain. The SH2 and SH3 domains work together in the auto-inhibition of the kinase domain. The phosphorylation of an inhibitory tyrosine near the c-terminus of the protein produces a binding site for the SH2 domain which then facilitates binding of the SH3 domain to a polyproline site within the linker between the SH2 domain and the kinase domain. Binding of the SH3 domain inactivates the enzyme. This allows for multiple mechanisms for c-Src activation: dephosphorylation of the C-terminal tyrosine by a protein tyrosine phosphatase, binding of the SH2 domain by a competitive phospho-tyrosine residue, or competitive binding of a polyproline binding site to the SH3 domain. Unlike most other Src members Src lacks cysteine residues in the SH4 domain that undergo palmitylation. Serine and threonine phosphorylation sites have also been identified in the unique domains of Src and are believed to modulate protein-protein interactions or regulate catalytic activity. Alternatively spliced forms of Src, which contain 6- or 11-amino acid insertions in the SH3 domain, are expressed in CNS neurons. c-Src has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10365     1 QAEEWYFGKITRRESERLLLNAENPRGTFLVRESETTKGAYCLSVSDFDNAKGLNVKHYKIRKLDSGGFYITSRTQFNSL 80

                          90       100
                  ....*....|....*....|.
gi 1907162151 232 QKLVKHYTEHADGLCHKLTTV 252
Cdd:cd10365    81 QQLVAYYSKHADGLCHRLTTV 101

Catalytic domain of the Protein Tyrosine Kinase, Src; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Src (or c-Src) is a cytoplasmic (or non-receptor) PTK, containing an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region with a conserved tyr. It is activated by autophosphorylation at the tyr kinase domain, and is negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). c-Src is the vertebrate homolog of the oncogenic protein (v-Src) from Rous sarcoma virus. Together with other Src subfamily proteins, it is involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. Src also play a role in regulating cell adhesion, invasion, and motility in cancer cells and tumor vasculature, contributing to cancer progression and metastasis. Elevated levels of Src kinase activity have been reported in a variety of human cancers. Several inhibitors of Src have been developed as anti-cancer drugs. Src is also implicated in acute inflammatory responses and osteoclast function. The Src subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 265 KDAWEIPRESLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEEPIYI 344
Cdd:cd05071     1 KDAWEIPRESLRLEVKLGQGCFGEVWMGTWNGTTRVAIKTLKPGTMSPEAFLQEAQVMKKLRHEKLVQLYAVVSEEPIYI 80

                  ....*..
gi 1907162151 345 VTEFMSK 351
Cdd:cd05071    81 VTEYMSK 87

Src homology 2 (SH2) domain found in HCK; HCK is a member of the Src non-receptor type tyrosine kinase family of proteins and is expressed in hemopoietic cells. HCK is proposed to couple the Fc receptor to the activation of the respiratory burst. It may also play a role in neutrophil migration and in the degranulation of neutrophils. It has two different translational starts that have different subcellular localization. HCK has been shown to interact with BCR gene, ELMO1 Cbl gene, RAS p21 protein activator 1, RASA3, Granulocyte colony-stimulating factor receptor, ADAM15 and RAPGEF1. Like the other members of the Src family the SH2 domain in addition to binding the target, also plays an autoinhibitory role by binding to its C-terminal tail. In general SH2 domains are involved in signal transduction. HCK has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10363     1 ETEEWFFKGISRKDAERQLLAPGNMLGSFMIRDSETTKGSYSLSVRDYDPQHGDTVKHYKIRTLDNGGFYISPRSTFSTL 80

                          90       100
                  ....*....|....*....|..
gi 1907162151 232 QKLVKHYTEHADGLCHKLTTVC 253
Cdd:cd10363    81 QELVDHYKKGNDGLCQKLSVPC 102

Catalytic domain of Src kinase-like Protein Tyrosine Kinases; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Src subfamily members include Src, Lck, Hck, Blk, Lyn, Fgr, Fyn, Yrk, and Yes. Src (or c-Src) proteins are cytoplasmic (or non-receptor) PTKs which are anchored to the plasma membrane. They contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. They were identified as the first proto-oncogene products, and they regulate cell adhesion, invasion, and motility in cancer cells and tumor vasculature, contributing to cancer progression and metastasis. Src kinases are overexpressed in a variety of human cancers, making them attractive targets for therapy. They are also implicated in acute inflammatory responses and osteoclast function. Src, Fyn, Yes, and Yrk are widely expressed, while Blk, Lck, Hck, Fgr, and Lyn show a limited expression pattern. The Src-like subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1907162151 280 KLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVS-EEPIYIVTEFMSK 351
Cdd:cd05034     2 KLGAGQFGEVWMGVWNGTTKVAVKTLKPGTMSPEAFLQEAQIMKKLRHDKLVQLYAVCSdEEPIYIVTELMSK 74

Src homology 2 (SH2) domain found in Lyn; Lyn is a member of the Src non-receptor type tyrosine kinase family of proteins and is expressed in the hematopoietic cells, in neural tissues, liver, and adipose tissue. There are two alternatively spliced forms of Lyn. Lyn plays an inhibitory role in myeloid lineage proliferation. Following engagement of the B cell receptors, Lyn undergoes rapid phosphorylation and activation, triggering a cascade of signaling events mediated by Lyn phosphorylation of tyrosine residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the receptor proteins, and subsequent recruitment and activation of other kinases including Syk, phospholipase C2 (PLC2) and phosphatidyl inositol-3 kinase. These kinases play critical roles in proliferation, Ca2+ mobilization and cell differentiation. Lyn plays an essential role in the transmission of inhibitory signals through phosphorylation of tyrosine residues within the immunoreceptor tyrosine-based inhibitory motifs (ITIM) in regulatory proteins such as CD22, PIR-B and FC RIIb1. Their ITIM phosphorylation subsequently leads to recruitment and activation of phosphatases such as SHIP-1 and SHP-1 which further down modulate signaling pathways, attenuate cell activation and can mediate tolerance. Lyn also plays a role in the insulin signaling pathway. Activated Lyn phosphorylates insulin receptor substrate 1 (IRS1) leading to an increase in translocation of Glut-4 to the cell membrane and increased glucose utilization. It is the primary Src family member involved in signaling downstream of the B cell receptor. Lyn plays an unusual, 2-fold role in B cell receptor signaling; it is essential for initiation of signaling but is also later involved in negative regulation of the signal. Lyn has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDWDEVRGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10364     1 ETEEWFFKDITRKDAERQLLAPGNSAGAFLIRESETLKGSYSLSVRDYDPQHGDVIKHYKIRSLDNGGYYISPRITFPCI 80

                          90
                  ....*....|....*...
gi 1907162151 232 QKLVKHYTEHADGLCHKL 249
Cdd:cd10364    81 SDMIKHYQKQSDGLCRRL 98

Catalytic domain of the Protein Tyrosine Kinases, Lymphocyte-specific kinase and Blk; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Lck and Blk are members of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. Lck is expressed in T-cells and natural killer cells. It plays a critical role in T-cell maturation, activation, and T-cell receptor (TCR) signaling. Lck phosphorylates ITAM (immunoreceptor tyr activation motif) sequences on several subunits of TCRs, leading to the activation of different second messenger cascades. Phosphorylated ITAMs serve as binding sites for other signaling factor such as Syk and ZAP-70, leading to their activation and propagation of downstream events. In addition, Lck regulates drug-induced apoptosis by interfering with the mitochondrial death pathway. The apototic role of Lck is independent of its primary function in T-cell signaling. Blk is expressed specifically in B-cells. It is involved in pre-BCR (B-cell receptor) signaling. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The Lck/Blk subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 268 WEIPRESLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEEPIYIVTE 347
Cdd:cd05067     2 WEVPRETLKLVERLGAGQFGEVWMGYYNGHTKVAIKSLKQGSMSPDAFLAEANLMKQLQHQRLVRLYAVVTQEPIYIITE 81

                  ....
gi 1907162151 348 FMSK 351
Cdd:cd05067    82 YMEN 85

Src homology 2 (SH2) domain found in the Src oncogene at 42A (Src42); Src42 is a member of the Src non-receptor type tyrosine kinase family of proteins. The integration of receptor tyrosine kinase-induced RAS and Src42 signals by Connector eNhancer of KSR (CNK) as a two-component input is essential for RAF activation in Drosophila. Src42 is present in a wide variety of organisms including: California sea hare, pea aphid, yellow fever mosquito, honey bee, Panamanian leafcutter ant, and sea urchin. Src42 has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Like the other members of the Src family the SH2 domain in addition to binding the target, also plays an autoinhibitory role by binding to its C-terminal tail. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDwdevrGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10370     1 EAEPWYFGKIKRIEAEKKLLLPENEHGAFLIRDSESRHNDYSLSVRD-----GDTVKHYRIRQLDEGGFFIARRTTFRTL 75

                          90
                  ....*....|....*...
gi 1907162151 232 QKLVKHYTEHADGLCHKL 249
Cdd:cd10370    76 QELVEHYSKDSDGLCVNL 93

Catalytic domain of the Protein Tyrosine Kinase, Hematopoietic cell kinase; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Hck is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. Hck is present in myeloid and lymphoid cells that play a role in the development of cancer. It may be important in the oncogenic signaling of the protein Tel-Abl, which induces a chronic myelogenous leukemia (CML)-like disease. Hck also acts as a negative regulator of G-CSF-induced proliferation of granulocytic precursors, suggesting a possible role in the development of acute myeloid leukemia (AML). In addition, Hck is essential in regulating the degranulation of polymorphonuclear leukocytes. Genetic polymorphisms affect the expression level of Hck, which affects PMN mediator release and influences the development of chronic obstructive pulmonary disease (COPD). Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The Hck subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 265 KDAWEIPRESLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEEPIYI 344
Cdd:cd05073     3 KDAWEIPRESLKLEKKLGAGQFGEVWMATYNKHTKVAVKTMKPGSMSVEAFLAEANVMKTLQHDKLVKLHAVVTKEPIYI 82

                  ....*..
gi 1907162151 345 VTEFMSK 351
Cdd:cd05073    83 ITEFMAK 89

Src homology 2 (SH2) domain found in the Fyn-related kinase (Frk); Frk is a member of the Src non-receptor type tyrosine kinase family of proteins. The Frk subfamily is composed of Frk/Rak and Iyk/Bsk/Gst. It is expressed primarily epithelial cells. Frk is a nuclear protein and may function during G1 and S phase of the cell cycle and suppress growth. Unlike the other Src members it lacks a glycine at position 2 of SH4 which is important for addition of a myristic acid moiety that is involved in targeting Src PTKs to cellular membranes. FRK and SHB exert similar effects when overexpressed in rat phaeochromocytoma (PC12) and beta-cells, where both induce PC12 cell differentiation and beta-cell proliferation. Under conditions that cause beta-cell degeneration these proteins augment beta-cell apoptosis. The FRK-SHB responses involve FAK and insulin receptor substrates (IRS) -1 and -2. Frk has been demonstrated to interact with retinoblastoma protein. Frk regulates PTEN protein stability by phosphorylating PTEN, which in turn prevents PTEN degradation. Frk also plays a role in regulation of embryonal pancreatic beta cell formation. Frk has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Like the other members of the Src family the SH2 domain in addition to binding the target, also plays an autoinhibitory role by binding to its activation loop. The tryosine involved is at the same site as the tyrosine involved in the autophosphorylation of Src. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIRDwdevrGDNVKHYKIRKLDNGGYYITTRAQFDTL 231
Cdd:cd10369     1 QAEPWFFGAIKRADAEKQLLYSENQTGAFLIRESESQKGEFSLSVLD-----GGVVKHYRIRRLDEGGFFLTRRKTFSTL 75

                          90
                  ....*....|....*...
gi 1907162151 232 QKLVKHYTEHADGLCHKL 249
Cdd:cd10369    76 NEFVNYYTTTSDGLCVKL 93

SH2 domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 156 WYFGKMGRKDAERLLLNpGNQRGIFLVRESETTKGAYSLSIRDWDevrgdNVKHYKIRKLDNGGYYITTRAQFDTLQKLV 235
Cdd:pfam00017   1 WYHGKISRQEAERLLLN-GKPDGTFLVRESESTPGGYTLSVRDDG-----KVKHYKIQSTDNGGYYISGGVKFSSLAELV 74

                  ...
gi 1907162151 236 KHY 238
Cdd:pfam00017  75 EHY 77

Src homology 3 domain of Src kinase-like Protein Tyrosine Kinases; Src subfamily members include Src, Lck, Hck, Blk, Lyn, Fgr, Fyn, Yrk, Yes, and Brk. Src (or c-Src) proteins are cytoplasmic (or non-receptor) PTKs which are anchored to the plasma membrane. They contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). However, Brk lacks the N-terminal myristoylation sites. Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. They were identified as the first proto-oncogene products, and they regulate cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Src kinases are overexpressed in a variety of human cancers, making them attractive targets for therapy. They are also implicated in acute inflammatory responses and osteoclast function. Src, Fyn, Yes, and Yrk are widely expressed, while Blk, Lck, Hck, Fgr, Lyn, and Brk show a limited expression pattern. This subfamily also includes Drosophila Src42A, Src oncogene at 42A (also known as Dsrc41) which accumulates at sites of cell-cell or cell-matrix adhesion, and participates in Drosphila development and wound healing. It has been shown to promote tube elongation in the tracheal system, is essential for proper cell-cell matching during dorsal closure, and regulates cell-cell contacts in developing Drosophila eyes. The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|..
gi 1907162151  93 IFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKSGYIPSNY 144
Cdd:cd11845     1 IYVALYDYEARTDDDLSFKKGDRLQILDDSDGDWWLARHLSTGKEGYIPSNY 52

Protein tyrosine and serine/threonine kinase; Protein phosphorylation, which plays a key role in most cellular activities, is a reversible process mediated by protein kinases and phosphoprotein phosphatases. Protein kinases catalyze the transfer of the gamma phosphate from nucleotide triphosphates (often ATP) to one or more amino acid residues in a protein substrate side chain, resulting in a conformational change affecting protein function. Phosphoprotein phosphatases catalyze the reverse process. Protein kinases fall into three broad classes, characterized with respect to substrate specificity; Serine/threonine-protein kinases, tyrosine-protein kinases, and dual specificity protein kinases (e.g. MEK - phosphorylates both Thr and Tyr on target proteins). This entry represents the catalytic domain found in a number of serine/threonine- and tyrosine-protein kinases. It does not include the catalytic domain of dual specificity kinases.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 275 LRLEVKLGQGCFGEVWMGTWNG-----TTKVAIKTLKPGTMMP--EAFLQEAQIMKKLRHDKLVPLYAVVS-EEPIYIVT 346
Cdd:pfam07714   1 LTLGEKLGEGAFGEVYKGTLKGegentKIKVAVKTLKEGADEEerEDFLEEASIMKKLDHPNIVKLLGVCTqGEPLYIVT 80

                  ...
gi 1907162151 347 EFM 349
Cdd:pfam07714  81 EYM 83

Src homology 3 domain of Src Protein Tyrosine Kinase; Src (or c-Src) is a cytoplasmic (or non-receptor) PTK and is the vertebrate homolog of the oncogenic protein (v-Src) from Rous sarcoma virus. Together with other Src subfamily proteins, it is involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. Src also play a role in regulating cell adhesion, invasion, and motility in cancer cells, and tumor vasculature, contributing to cancer progression and metastasis. Elevated levels of Src kinase activity have been reported in a variety of human cancers. Several inhibitors of Src have been developed as anti-cancer drugs. Src is also implicated in acute inflammatory responses and osteoclast function. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*
gi 1907162151  94 FVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIATGKSGYIPSNYVVPA 148
Cdd:cd12008     2 FVALYDYESRTETDLSFKKGERLQIVNNTEGDWWLAHSLTTGQTGYIPSNYVAPS 56

Tyrosine kinase, catalytic domain; Phosphotransferases. Tyrosine-specific kinase subfamily.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151  275 LRLEVKLGQGCFGEVWMGTWNGT-----TKVAIKTLKPGTMMP--EAFLQEAQIMKKLRHDKLVPLYAVVSE-EPIYIVT 346
Cdd:smart00219   1 LTLGKKLGEGAFGEVYKGKLKGKggkkkVEVAVKTLKEDASEQqiEEFLREARIMRKLDHPNVVKLLGVCTEeEPLYIVM 80

                   ....*
gi 1907162151  347 EFMSK 351
Cdd:smart00219  81 EYMEG 85

Catalytic domain of C-terminal Src kinase-like Protein Tyrosine Kinases; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. This subfamily is composed of Csk, Chk, and similar proteins. They are cytoplasmic (or nonreceptor) PTKs containing the Src homology domains, SH3 and SH2, N-terminal to the catalytic tyr kinase domain. They negatively regulate the activity of Src kinases that are anchored to the plasma membrane. To inhibit Src kinases, Csk and Chk are translocated to the membrane via binding to specific transmembrane proteins, G-proteins, or adaptor proteins near the membrane. Csk catalyzes the tyr phosphorylation of the regulatory C-terminal tail of Src kinases, resulting in their inactivation. Chk inhibit Src kinases using a noncatalytic mechanism by simply binding to them. As negative regulators of Src kinases, Csk and Chk play important roles in cell proliferation, survival, and differentiation, and consequently, in cancer development and progression. The Csk-like subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 268 WEIPRESLRLEVKLGQGCFGEVWMGTWNGTtKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEE-PIYIVT 346
Cdd:cd05039     1 WAINKKDLKLGELIGKGEFGDVMLGDYRGQ-KVAVKCLKDDSTAAQAFLAEASVMTTLRHPNLVQLLGVVLEGnGLYIVT 79

                  ....*
gi 1907162151 347 EFMSK 351
Cdd:cd05039    80 EYMAK 84

Catalytic domain of Protein Tyrosine Kinases; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. They can be classified into receptor and non-receptor tyr kinases. PTKs play important roles in many cellular processes including, lymphocyte activation, epithelium growth and maintenance, metabolism control, organogenesis regulation, survival, proliferation, differentiation, migration, adhesion, motility, and morphogenesis. Receptor tyr kinases (RTKs) are integral membrane proteins which contain an extracellular ligand-binding region, a transmembrane segment, and an intracellular tyr kinase domain. RTKs are usually activated through ligand binding, which causes dimerization and autophosphorylation of the intracellular tyr kinase catalytic domain, leading to intracellular signaling. Some RTKs are orphan receptors with no known ligands. Non-receptor (or cytoplasmic) tyr kinases are distributed in different intracellular compartments and are usually multi-domain proteins containing a catalytic tyr kinase domain as well as various regulatory domains such as SH3 and SH2. PTKs are usually autoinhibited and require a mechanism for activation. In many PTKs, the phosphorylation of tyr residues in the activation loop is essential for optimal activity. Aberrant expression of PTKs is associated with many development abnormalities and cancers.The PTK family is part of a larger superfamily that includes the catalytic domains of serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1907162151 280 KLGQGCFGEVWMGTW----NGTTKVAIKTLKPGTMMPE--AFLQEAQIMKKLRHDKLVPLYAV-VSEEPIYIVTEFMS 350
Cdd:cd00192     2 KLGEGAFGEVYKGKLkggdGKTVDVAVKTLKEDASESErkDFLKEARVMKKLGHPNVVRLLGVcTEEEPLYLVMEYME 79

Catalytic domain of Tec-like Protein Tyrosine Kinases; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. The Tec-like subfamily is composed of Tec, Btk, Bmx (Etk), Itk (Tsk, Emt), Rlk (Txk), and similar proteins. They are cytoplasmic (or nonreceptor) PTKs with similarity to Src kinases in that they contain Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Unlike Src kinases, most Tec subfamily members except Rlk also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. In addition, some members contain the Tec homology (TH) domain, which contains proline-rich and zinc-binding regions. Tec kinases form the second largest subfamily of nonreceptor PTKs and are expressed mainly by haematopoietic cells, although Tec and Bmx are also found in endothelial cells. B-cells express Btk and Tec, while T-cells express Itk, Txk, and Tec. Collectively, Tec kinases are expressed in a variety of myeloid cells such as mast cells, platelets, macrophages, and dendritic cells. Each Tec kinase shows a distinct cell-type pattern of expression. Tec kinases play important roles in the development, differentiation, maturation, regulation, survival, and function of B-cells and T-cells. Mutations in Btk cause the severe B-cell immunodeficiency, X-linked agammaglobulinaemia (XLA). The Tec-like subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1907162151 274 SLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEE-PIYIVTEFM 349
Cdd:cd05059     5 ELTFLKELGSGQFGVVHLGKWRGKIDVAIKMIKEGSMSEDDFIEEAKVMMKLSHPKLVQLYGVCTKQrPIFIVTEYM 81

Catalytic domain of the Protein Tyrosine Kinases, Bruton's tyrosine kinase and Bone marrow kinase on the X chromosome; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Btk and Bmx (also named Etk) are members of the Tec-like subfamily of proteins, which are cytoplasmic (or nonreceptor) PTKs with similarity to Src kinases in that they contain Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Unlike Src kinases, most Tec subfamily members except Rlk also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. In addition, Btk contains the Tec homology (TH) domain with proline-rich and zinc-binding regions. Btk is expressed in B-cells, and a variety of myeloid cells including mast cells, platelets, neutrophils, and dendrictic cells. It interacts with a variety of partners, from cytosolic proteins to nuclear transcription factors, suggesting a diversity of functions. Stimulation of a diverse array of cell surface receptors, including antigen engagement of the B-cell receptor, leads to PH-mediated membrane translocation of Btk and subsequent phosphorylation by Src kinase and activation. Btk plays an important role in the life cycle of B-cells including their development, differentiation, proliferation, survival, and apoptosis. Mutations in Btk cause the primary immunodeficiency disease, X-linked agammaglobulinaemia (XLA) in humans. Bmx is primarily expressed in bone marrow and the arterial endothelium, and plays an important role in ischemia-induced angiogenesis. It facilitates arterial growth, capillary formation, vessel maturation, and bone marrow-derived endothelial progenitor cell mobilization. The Btk/Bmx subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 270 IPRESLRLEVKLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEE-PIYIVTEF 348
Cdd:cd05113     1 IDPKDLTFLKELGTGQFGVVKYGKWRGQYDVAIKMIKEGSMSEDEFIEEAKVMMNLSHEKLVQLYGVCTKQrPIFIITEY 80

                  ..
gi 1907162151 349 MS 350
Cdd:cd05113    81 MA 82

N-terminal Src homology 2 (N-SH2) domain in Phospholipase C gamma; Phospholipase C gamma is a signaling molecule that is recruited to the C-terminal tail of the receptor upon autophosphorylation of a highly conserved tyrosine. PLCgamma is composed of a Pleckstrin homology (PH) domain followed by an elongation factor (EF) domain, 2 catalytic regions of PLC domains that flank 2 tandem SH2 domains (N-SH2, C-SH2), and ending with a SH3 domain and C2 domain. N-SH2 SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. Both N-SH2 and C-SH2 have a very similar binding affinity to pY. But in growth factor stimulated cells these domains bind to different target proteins. N-SH2 binds to pY containing sites in the C-terminal tails of tyrosine kinases and other receptors. Recently it has been shown that this interaction is mediated by phosphorylation-independent interactions between a secondary binding site found exclusively on the N-SH2 domain and a region of the FGFR1 tyrosine kinase domain. This secondary site on the SH2 cooperates with the canonical pY site to regulate selectivity in mediating a specific cellular process. C-SH2 binds to an intramolecular site on PLCgamma itself which allows it to hydrolyze phosphatidylinositol-4,5-bisphosphate into diacylglycerol and inositol triphosphate. These then activate protein kinase C and release calcium. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 152 QAEEWYFGKM--GRKDAERLLL--NPGNQrGIFLVRESETTKGAYSLSIrdWdevRGDNVKHYKIRKLDNGG---YYITT 224
Cdd:cd10341     2 FTEPWFHGKLgdGRDEAEKLLLeyCEGGD-GTFLVRESETFVGDYTLSF--W---RNGKVQHCRIRSRQENGekkYYLTD 75

                          90
                  ....*....|....*..
gi 1907162151 225 RAQFDTLQKLVKHYTEH 241
Cdd:cd10341    76 NLVFDSLYELIDYYRQN 92

Src homology 3 domains; Src homology 3 (SH3) domains bind to target proteins through sequences containing proline and hydrophobic amino acids. Pro-containing polypeptides may bind to SH3 domains in 2 different binding orientations.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*.
gi 1907162151   90 GVTIFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIaTGKSGYIPSNYV 145
Cdd:smart00326   1 EGPQVRALYDYTAQDPDELSFKKGDIITVLEKSDDGWWKGRLG-RGKEGLFPSNYV 55

Catalytic domain of the Protein Tyrosine Kinases, Tyrosine kinase expressed in hepatocellular carcinoma and Resting lymphocyte kinase; PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Tec and Rlk (also named Txk) are members of the Tec-like subfamily of proteins, which are cytoplasmic (or nonreceptor) PTKs with similarity to Src kinases in that they contain Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Unlike Src kinases, most Tec subfamily members except Rlk also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. Instead of PH, Rlk contains an N-terminal cysteine-rich region. In addition to PH, Tec also contains the Tec homology (TH) domain with proline-rich and zinc-binding regions. Tec kinases are expressed mainly by haematopoietic cells. Tec is more widely-expressed than other Tec-like subfamily kinases. It is found in endothelial cells, both B- and T-cells, and a variety of myeloid cells including mast cells, erythroid cells, platelets, macrophages and neutrophils. Rlk is expressed in T-cells and mast cell lines. Tec and Rlk are both key components of T-cell receptor (TCR) signaling. They are important in TCR-stimulated proliferation, IL-2 production and phopholipase C-gamma1 activation. The Tec/Rlk subfamily is part of a larger superfamily, that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1907162151 280 KLGQGCFGEVWMGTWNGTTKVAIKTLKPGTMMPEAFLQEAQIMKKLRHDKLVPLYAVVSEE-PIYIVTEFM 349
Cdd:cd05114    11 ELGSGLFGVVRLGKWRAQYKVAIKAIREGAMSEEDFIEEAKVMMKLTHPKLVQLYGVCTQQkPIYIVTEFM 81

Catalytic domain of Mitogen-Activated Protein Kinase (MAPK) Kinase Kinase-like Serine/Threonine kinases; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily is composed mainly of MAP3Ks and similar proteins, including TGF-beta Activated Kinase-1 (TAK1, also called MAP3K7), MAP3K12, MAP3K13, Mixed lineage kinase (MLK), MLK-Like mitogen-activated protein Triple Kinase (MLTK), and Raf (Rapidly Accelerated Fibrosarcoma) kinases. MAP3Ks (MKKKs or MAPKKKs) phosphorylate and activate MAPK kinases (MAPKKs or MKKs or MAP2Ks), which in turn phosphorylate and activate MAPKs during signaling cascades that are important in mediating cellular responses to extracellular signals. Also included in this subfamily is the pseudokinase Kinase Suppressor of Ras (KSR), which is a scaffold protein that functions downstream of Ras and upstream of Raf in the Extracellular signal-Regulated Kinase (ERK) pathway.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1907162151 281 LGQGCFGEVWMGTWNGtTKVAIKTLKPGTMMP---EAFLQEAQIMKKLRHDKLVPLYAVVSEEP-IYIVTEFMS 350
Cdd:cd13999     1 IGSGSFGEVYKGKWRG-TDVAIKKLKVEDDNDellKEFRREVSILSKLRHPNIVQFIGACLSPPpLCIVTEYMP 73

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*...
gi 1907162151  95 VALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARSIaTGKSGYIPS 142
Cdd:pfam00018   1 VALYDYTAQEPDELSFKKGDIIIVLEKSEDGWWKGRNK-GGKEGLIPS 47

Src Homology 3 domain superfamily; Src Homology 3 (SH3) domains are protein interaction domains that bind proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. Thus, they are referred to as proline-recognition domains (PRDs). SH3 domains are less selective and show more diverse specificity compared to other PRDs. They have been shown to bind peptide sequences that lack the PxxP motif; examples include the PxxDY motif of Eps8 and the RKxxYxxY sequence in SKAP55. SH3 domain containing proteins play versatile and diverse roles in the cell, including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies, among others. Many members of this superfamily are adaptor proteins that associate with a number of protein partners, facilitating complex formation and signal transduction.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|..
gi 1907162151  93 IFVALYDYEARTTEDLSFKKGERFQIINNTEGDWWEARsIATGKSGYIPSNY 144
Cdd:cd00174     1 YARALYDYEAQDDDELSFKKGDIITVLEKDDDGWWEGE-LNGGREGLFPANY 51

C-terminal Src homology 2 (C-SH2) domain found in SH2 domain Phosphatases (SHP) proteins; The SH2 domain phosphatases (SHP-1, SHP-2/Syp, Drosophila corkscrew (csw), and Caenorhabditis elegans Protein Tyrosine Phosphatase (Ptp-2)) are cytoplasmic signaling enzymes. They are both targeted and regulated by interactions of their SH2 domains with phosphotyrosine docking sites. These proteins contain two SH2 domains (N-SH2, C-SH2) followed by a tyrosine phosphatase (PTP) domain, and a C-terminal extension. Shp1 and Shp2 have two tyrosyl phosphorylation sites in their C-tails, which are phosphorylated differentially by receptor and nonreceptor PTKs. Csw retains the proximal tyrosine and Ptp-2 lacks both sites. Shp-binding proteins include receptors, scaffolding adapters, and inhibitory receptors. Some of these bind both Shp1 and Shp2 while others bind only one. Most proteins that bind a Shp SH2 domain contain one or more immuno-receptor tyrosine-based inhibitory motifs (ITIMs): [SIVL]xpYxx[IVL]. Shp1 N-SH2 domain blocks the catalytic domain and keeps the enzyme in the inactive conformation, and is thus believed to regulate the phosphatase activity of SHP-1. Its C-SH2 domain is thought to be involved in searching for phosphotyrosine activators. The SHP2 N-SH2 domain is a conformational switch; it either binds and inhibits the phosphatase, or it binds phosphoproteins and activates the enzyme. The C-SH2 domain contributes binding energy and specificity, but it does not have a direct role in activation. Csw SH2 domain function is essential, but either SH2 domain can fulfill this requirement. The role of the csw SH2 domains during Sevenless receptor tyrosine kinase (SEV) signaling is to bind Daughter of Sevenless rather than activated SEV. Ptp-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote major sperm protein (MSP)-induced MAP Kinase (MPK-1) phosphorylation. Ptp-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. It is thought that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation and that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 156 WYFGKMGRKDAERLLLNPGnQRGIFLVRESETTKGAYSLSIRdwdeVRGDNVKHYKIRkLDNGGYYITTRAQFDTLQKLV 235
Cdd:cd09931     2 WFHGHLSGKEAEKLLLEKG-KPGSFLVRESQSKPGDFVLSVR----TDDDKVTHIMIR-CQGGKYDVGGGEEFDSLTDLV 75

                  ....*.
gi 1907162151 236 KHYTEH 241
Cdd:cd09931    76 EHYKKN 81

N-terminal Src homology 2 (SH2) domain found in Zeta-chain-associated protein kinase 70 (ZAP-70) and Spleen tyrosine kinase (Syk) proteins; ZAP-70 and Syk comprise a family of hematopoietic cell specific protein tyrosine kinases (PTKs) that are required for antigen and antibody receptor function. ZAP-70 is expressed in T and natural killer (NK) cells and Syk is expressed in B cells, mast cells, polymorphonuclear leukocytes, platelets, macrophages, and immature T cells. They are required for the proper development of T and B cells, immune receptors, and activating NK cells. They consist of two N-terminal Src homology 2 (SH2) domains and a C-terminal kinase domain separated from the SH2 domains by a linker or hinge region. Phosphorylation of both tyrosine residues within the Immunoreceptor Tyrosine-based Activation Motifs (ITAM; consensus sequence Yxx[LI]x(7,8)Yxx[LI]) by the Src-family PTKs is required for efficient interaction of ZAP-70 and Syk with the receptor subunits and for receptor function. ZAP-70 forms two phosphotyrosine binding pockets, one of which is shared by both SH2 domains. In Syk the two SH2 domains do not form such a phosphotyrosine-binding site. The SH2 domains here are believed to function independently. In addition, the two SH2 domains of Syk display flexibility in their relative orientation, allowing Syk to accommodate a greater variety of spacing sequences between the ITAM phosphotyrosines and singly phosphorylated non-classical ITAM ligands. This model contains the N-terminus SH2 domains of both Syk and Zap70. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907162151 156 WYFGKMGRKDAERLLLNPGNQRGIFLVRESETTKGAYSLSIrdwdeVRGDNVKHYKIRKLDNGGYYITTRAQFDTLQKLV 235
Cdd:cd09938     3 FFYGSITREEAEEYLKLAGMSDGLFLLRQSLRSLGGYVLSV-----CHGRKFHHYTIERQLNGTYAIAGGKAHCGPAELC 77