Immunoglobulin Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins; The members here are composed of the Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins. CAR, which is encoded by human CXADR gene, is a cell adhesion molecule of the Immunoglobulin (Ig) superfamily. The CAR acts as a type I membrane receptor for group B1-B6 coxsackie viruses and subgroup C adenoviruses. For instance, adenovirus interacts with the coxsackievirus and adenovirus receptor to enter epithelial airway cells. The CAR is also shown to be involved in physiological processes such as neuronal and heart development, epithelial tight junction integrity, and tumor suppression. The CAR is a component of the epithelial apical junction complex that may function as a homophilic cell adhesion molecule and is essential for tight junction integrity. The CAR is also involved in transepithelial migration of leukocytes through adhesive interactions with JAML a transmembrane protein of the plasma membrane of leukocytes. The interaction between both receptors also mediates the activation of gamma-delta T-cells, a subpopulation of T-cells residing in epithelia and involved in tissue homeostasis and repair. The CAR is composed of one V-set and one C2-set Ig module, a single transmembrane helix, and an intracellular domain. This group belongs to the V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  20 LSITTPEEMIEKAKGETAYLPCKFTLSPEDQGPLDIEWLISPADnqKVDQVIILYSGDKIYDDYYPDLKGRVHFTSNDlK 99
Cdd:cd20960    1 LLITSAQTEIKKVAGENVTLPCHHQLGLEDQGTLDIEWLLLPSD--KVEKVVITYSGDRVYNHYYPALKGRVAFTSND-L 77

                         90       100       110
                 ....*....|....*....|....*....|....*..
gi 768020327 100 SGDASINVTNLQLSDIGTYQCKVKKAPGVANKKIHLV 136
Cdd:cd20960   78 SGDASLNISNLKLSDTGTYQCKVKKAPGYAWSKITLI 114

Immunoglobulin Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins; The members here are composed of the Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins. CAR, which is encoded by human CXADR gene, is a cell adhesion molecule of the Immunoglobulin (Ig) superfamily. The CAR acts as a type I membrane receptor for group B1-B6 coxsackie viruses and subgroup C adenoviruses. For instance, adenovirus interacts with the coxsackievirus and adenovirus receptor to enter epithelial airway cells. The CAR is also shown to be involved in physiological processes such as neuronal and heart development, epithelial tight junction integrity, and tumor suppression. The CAR is a component of the epithelial apical junction complex that may function as a homophilic cell adhesion molecule and is essential for tight junction integrity. The CAR is also involved in transepithelial migration of leukocytes through adhesive interactions with JAML a transmembrane protein of the plasma membrane of leukocytes. The interaction between both receptors also mediates the activation of gamma-delta T-cells, a subpopulation of T-cells residing in epithelia and involved in tissue homeostasis and repair. The CAR is composed of one V-set and one C2-set Ig module, a single transmembrane helix, and an intracellular domain. This group belongs to the V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  20 LSITTPEEMIEKAKGETAYLPCKFTLSPEDQGPLDIEWLISPADnqKVDQVIILYSGDKIYDDYYPDLKGRVHFTSNDlK 99
Cdd:cd20960    1 LLITSAQTEIKKVAGENVTLPCHHQLGLEDQGTLDIEWLLLPSD--KVEKVVITYSGDRVYNHYYPALKGRVAFTSND-L 77

                         90       100       110
                 ....*....|....*....|....*....|....*..
gi 768020327 100 SGDASINVTNLQLSDIGTYQCKVKKAPGVANKKIHLV 136
Cdd:cd20960   78 SGDASLNISNLKLSDTGTYQCKVKKAPGYAWSKITLI 114

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327    29 IEKAKGETAYLPCKFTLSPEDQgpldIEWLispadnqKVDQVIILYSGdkiyddyypdlkgRVHFTSNdlkSGDASINVT 108
Cdd:smart00410   4 VTVKEGESVTLSCEASGSPPPE----VTWY-------KQGGKLLAESG-------------RFSVSRS---GSTSTLTIS 56

                           90       100
                   ....*....|....*....|....*....
gi 768020327   109 NLQLSDIGTYQCKVKKAPGVANKKIHLVV 137
Cdd:smart00410  57 NVTPEDSGTYTCAATNSSGSASSGTTLTV 85

Immunoglobulin Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins; The members here are composed of the Variable (V) domain of the Coxsackievirus and Adenovirus Receptor (CAR), and similar proteins. CAR, which is encoded by human CXADR gene, is a cell adhesion molecule of the Immunoglobulin (Ig) superfamily. The CAR acts as a type I membrane receptor for group B1-B6 coxsackie viruses and subgroup C adenoviruses. For instance, adenovirus interacts with the coxsackievirus and adenovirus receptor to enter epithelial airway cells. The CAR is also shown to be involved in physiological processes such as neuronal and heart development, epithelial tight junction integrity, and tumor suppression. The CAR is a component of the epithelial apical junction complex that may function as a homophilic cell adhesion molecule and is essential for tight junction integrity. The CAR is also involved in transepithelial migration of leukocytes through adhesive interactions with JAML a transmembrane protein of the plasma membrane of leukocytes. The interaction between both receptors also mediates the activation of gamma-delta T-cells, a subpopulation of T-cells residing in epithelia and involved in tissue homeostasis and repair. The CAR is composed of one V-set and one C2-set Ig module, a single transmembrane helix, and an intracellular domain. This group belongs to the V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  20 LSITTPEEMIEKAKGETAYLPCKFTLSPEDQGPLDIEWLISPADnqKVDQVIILYSGDKIYDDYYPDLKGRVHFTSNDlK 99
Cdd:cd20960    1 LLITSAQTEIKKVAGENVTLPCHHQLGLEDQGTLDIEWLLLPSD--KVEKVVITYSGDRVYNHYYPALKGRVAFTSND-L 77

                         90       100       110
                 ....*....|....*....|....*....|....*..
gi 768020327 100 SGDASINVTNLQLSDIGTYQCKVKKAPGVANKKIHLV 136
Cdd:cd20960   78 SGDASLNISNLKLSDTGTYQCKVKKAPGYAWSKITLI 114

Immunoglobulin (Ig)-like domain of protein zero (P0) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of protein zero (P0), a myelin membrane adhesion molecule. P0 accounts for over 50% of the total protein in peripheral nervous system (PNS) myelin. P0 is a single-pass transmembrane glycoprotein with a highly basic intracellular domain and an extracellular Ig domain. The extracellular domain of P0 (P0-ED) is similar to the Ig variable domain, carrying one acceptor sequence for N-linked glycosylation. P0 plays a role in membrane adhesion in the spiral wraps of the myelin sheath. The intracellular domain is thought to mediate membrane apposition of the cytoplasmic faces and may, through electrostatic interactions, interact directly with lipid headgroups. It is thought that homophilic interactions of the P0 extracellular domain mediate membrane juxtaposition in the extracellular space of PNS myelin. This group also contains the Ig domain of sodium channel subunit beta-2 (SCN2B), and of epithelial V-like antigen 1 (EVA). EVA, also known as myelin protein zero-like 2, is an adhesion molecule, which may play a role in structural organization of the thymus and early lymphocyte development. SCN2B subunits play a role in determining sodium channel density and function in neurons,and in control of electrical excitability in the brain.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  20 LSITTPEEmIEKAKGETAYLPCKFTLSPEDQGPLDIEWLISPaDNQKVDQVIILYSGDKIYDDYYPDLKGRVHFTSNdLK 99
Cdd:cd05715    1 MEVYTPRE-LNVLNGSDVRLTCTFTSCYTVGDAFSVTWTYQP-EGGNTTESMFHYSKGKPYILKVGRFKDRVSWAGN-PS 77

                         90       100       110       120
                 ....*....|....*....|....*....|....*....|
gi 768020327 100 SGDASINVTNLQLSDIGTYQCKVKKAPGVANK--KIHLVV 137
Cdd:cd05715   78 KKDASIVISNLQFSDNGTYTCDVKNPPDIVGGhgEIRLYV 117

Immunoglobulin Variable (IgV) domain of B7-H4; The members here are composed of the immunoglobulin variable (IgV) domain of B7-H4 (also known as B7-S1, B7x, or Vtcn1). B7-H4 is one of the B7 family of immune-regulatory ligands that act as negative regulators of T cell function; it contains one IgV domain and one IgC domain. The B7-family consists of structurally related cell-surface protein ligands, which bind to receptors on lymphocytes that regulate immune responses. The binding of B7-H4 to unidentified receptors results in the inhibition of TCR-mediated T cell proliferation, cell-cycle progression and IL-2 production. As a co-inhibitory molecule, B7-H4 is widely expressed in tumor tissues and its expression is significantly associated with poor prognosis in human cancers such as glioma, pancreatic cancer, oral squamous cell carcinoma, renal cell carcinoma, and lung cancer.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  34 GETAYLPCKFTLSPEDQGpLDIEWLiSPADNQKVDQviiLYSGDKIYDDYYPDLKGRVHFTSNDLKSGDASINVTNLQLS 113
Cdd:cd20984   12 GEDGILSCTFTPDIKLSD-IVIQWL-KEGDSGLVHE---FKEGKDELSRQSPMFRGRTSLFADQVHVGNASLRLKNVQLT 86

                         90       100
                 ....*....|....*....|
gi 768020327 114 DIGTYQCKVKKAPGVANKKI 133
Cdd:cd20984   87 DAGTYLCIISNSKGTGNANM 106

Immunoglobulin (Ig)-like domain of chondroitin sulfate proteoglycans (CSPGs), human cartilage link protein (LP), and similar domains; The members here are composed of the immunoglobulin (Ig)-like domain similar to that found in chondroitin sulfate proteoglycans (CSPGs) and human cartilage link protein (LP). Included in this group are the CSPGs aggrecan, versican, and neurocan. In CSPGs, this Ig-like domain is followed by hyaluronan (HA)-binding tandem repeats, and a C-terminal region with epidermal growth factor-like, lectin-like, and complement regulatory protein-like domains. Separating these N- and C-terminal regions is a nonhomologous glycosaminoglycan attachment region. In cartilage, aggrecan forms cartilage link protein stabilized aggregates with hyaluronan (HA). These aggregates contribute to the tissue's load bearing properties. Aggrecan and versican have a wide distribution in connective tissue and extracellular matrices. Neurocan is localized almost exclusively in nervous tissue. Aggregates having other CSPGs substituting for aggrecan may contribute to the structural integrity of many different tissues. There is considerable evidence that HA-binding CSPGs are involved in developmental processes in the central nervous system. Members of the vertebrate HPLN (hyaluronan/HA and proteoglycan binding link) protein family are physically linked adjacent to CSPG genes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  29 IEKAKGETAYLPCKFTLSPEDQGP----LDIEWLISPADNQKVDQVIILYSGD---KIYDDYypdlKGRVHFTSNDLKSG 101
Cdd:cd05714    7 VFSHLGGNVTLPCKFYRDPTAFGSgihkIRIKWTKLTSDSGYLKEVDVLVAMGnvvYHKKTY----GGRVSVPLKPGSDS 82

                         90       100
                 ....*....|....*....|.
gi 768020327 102 DASINVTNLQLSDIGTYQCKV 122
Cdd:cd05714   83 DASLVITDLTASDYGLYRCEV 103

Immunoglobulin variable domain (IgV) in Cluster of Differentiation (CD) 80; The members here are composed of the immunoglobulin variable region (IgV) in the Cluster of Differentiation (CD) 80). Glycoproteins B7-1 (also known as cluster of differentiation (CD) 80) and B7-2 (also known as CD86) are expressed on antigen-presenting cells and deliver the co-stimulatory signal through CD28 and CTLA-4 (also known as cluster of differentiation 152/CD152) on T cells. signaling through CD28 augments the T-cell response, whereas CTLA-4 signaling attenuates it. CD80 contains two Ig-like domains, an amino-terminal immunoglobulin variable (IgV)-like domain characteristic of adhesion molecules and a membrane proximal immunoglobulin constant (IgC)-like domain similar to the constant domains of antigen receptors. Members of the Ig family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and Major Histocompatibility Complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  29 IEKAKGETAYLPCKFTLSPEDQGPLDIEWlispadnQKVDQVII-LYSGDKiydDYYPDLKGRvhfTSNDLkSGDASINV 107
Cdd:cd16086    4 VTKSVKEKALLSCDYNVSVDELAQVRIYW-------QKDDKMVLtIISGDV---KVWPEYKNR---TLFDI-TNNLSIVI 69

                         90       100
                 ....*....|....*....|....*....
gi 768020327 108 TNLQLSDIGTYQCKVKKAPGVANKKIHLV 136
Cdd:cd16086   70 LALRLSDRGTYTCVVQKKERGAYKREHLA 98

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327    29 IEKAKGETAYLPCKFTLSPEDQgpldIEWLispadnqKVDQVIILYSGdkiyddyypdlkgRVHFTSNdlkSGDASINVT 108
Cdd:smart00410   4 VTVKEGESVTLSCEASGSPPPE----VTWY-------KQGGKLLAESG-------------RFSVSRS---GSTSTLTIS 56

                           90       100
                   ....*....|....*....|....*....
gi 768020327   109 NLQLSDIGTYQCKVKKAPGVANKKIHLVV 137
Cdd:smart00410  57 NVTPEDSGTYTCAATNSSGSASSGTTLTV 85

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327    36 TAYLPCKFTLSpeDQGPLDIEWLISPADNQkvdqVIILYSGDKIYDDYYPD-LKGRVHFtSNDLKSGDASINVTNLQLSD 114
Cdd:smart00406   1 SVTLSCKFSGS--TFSSYYVSWVRQPPGKG----LEWLGYIGSNGSSYYQEsYKGRFTI-SKDTSKNDVSLTISNLRVED 73

                   ....*...
gi 768020327   115 IGTYQCKV 122
Cdd:smart00406  74 TGTYYCAV 81

Immunoglobulin variable domain (IgV) in Cluster of Differentiation (CD) 86; The members here are composed of the immunoglobulin variable region (IgV) in the Cluster of Differentiation (CD) 86). Glycoproteins B7-1 (also known as cluster of differentiation (CD) 80) and B7-2 (also known as CD86) are expressed on antigen-presenting cells and deliver the co-stimulatory signal through CD28 and CTLA-4 (also known as CD152) on T cells. signaling through CD28 augments the T-cell response, whereas CTLA-4 signaling attenuates it. The CTLA-4 and B7-2 monomers are both two-layer beta-sandwiches that display the chain topology characteristic of the immunoglobulin variable (V-type) domains present in antigen receptors. The front and back sheets of B7-2 are composed of AGFCC'C" and BED strands, respectively. Members of the IgV family are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 beta-sheets with a tryptophan residue packed against the disulfide bond.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  34 GETAYLPCKFTlSPEDqgpLDIEWLISPADNQKVDQVIILYSGDKIYDDYYPDLKGRVHFTSNDLksgdaSINVTNLQLS 113
Cdd:cd16087    8 NETAYLPCQFK-NPQN---ISLSELVVFWQDQKKLVLYELYLGKEKLDNVNSKYIGRTSFDQENW-----TLQLHNVQIK 78

                         90       100
                 ....*....|....*....|.
gi 768020327 114 DIGTYQCKVKKAPGVANKKIH 134
Cdd:cd16087   79 DQGTYQCFIHHKSPKGLVLIH 99

First immunoglobulin variable (IgV) domain of poliovirus receptor (PVR, also known as CD155 and necl-5), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (necl-5)). Poliovirus (PV) binds to its cellular receptor (PVR/CD155) to initiate infection. CD155 is a membrane-anchored, single-span glycoprotein; its extracellular region has three Ig-like domains. There are four different isotypes of CD155 (referred to as alpha, beta, gamma, and delta), that result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted; CD155-alpha and CD155-delta are membrane-bound and function as PV receptors. The virus recognition site is contained in the amino-terminal domain, D1. Having the virus attachment site on the receptor distal from the plasma membrane may be important for successful initiation of infection of cells by the virus. CD155 binds in the poliovirus "canyon" with a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the first Ig-like domain of nectin-1 (also known as poliovirus receptor related protein(PVRL)1; CD111), nectin-3 (also known as PVRL 3), nectin-4 (also known as PVRL4; LNIR receptor)and DNAX accessory molecule 1 (DNAM-1; CD226).

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  34 GETAYLPCKFTlSPEDQGPLDIEWLISPADNQkvdQVIILYS---GDKIYDDYypdlKGRVHFTSNDLKSGDASINVTNL 110
Cdd:cd05718   14 GGSVTLPCSLT-SPGTTKITQVTWMKIGAGSS---QNVAVFHpqyGPSVPNPY----AERVEFLAARLGLRNATLRIRNL 85

                         90       100
                 ....*....|....*....|....*...
gi 768020327 111 QLSDIGTYQCKVKKAP-GVANKKIHLVV 137
Cdd:cd05718   86 RVEDEGNYICEFATFPqGNRQGTTWLRV 113

Immunoglobulin (Ig)-like domain of the chondroitin sulfate proteoglycan core protein (CSPG), versican; The members here are composed of the immunoglobulin (Ig)-like domain of the chondroitin sulfate proteoglycan core protein (CSPG), versican. In CSPGs, the Ig-like domain is followed by hyaluronan (HA)-binding tandem repeats, and a C-terminal region with epidermal growth factor-like, lectin-like, and complement regulatory protein-like domains. Separating these N- and C-terminal regions is a nonhomologous glycosaminoglycan attachment region. In cartilage, the CSPG aggrecan (not included in this group) forms cartilage link protein stabilized aggregates with HA. These aggregates contribute to the tissue's load bearing properties. Like aggrecan, versican has a wide distribution in connective tissue and extracellular matrices. Aggregates having other CSPGs substituting for aggrecan may contribute to the structural integrity of many different tissues. Members of the vertebrate HPLN (hyaluronan/HA and proteoglycan binding link) protein family are physically linked adjacent to CSPG genes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  39 LPCKFTLSPEDQGP-------LDIEWLISPADNQKVDQ----VIILYSGD-KIYDDYypdlKGRVHFTSNDLKSGDASIN 106
Cdd:cd05901   17 LPCRFSTLPTLPPSynitsefLRIKWTKIQVDKNGKDHkettVLVAQNGIiKIGQEY----MGRVSVPSHPEDQGDASLT 92

                         90
                 ....*....|....*.
gi 768020327 107 VTNLQLSDIGTYQCKV 122
Cdd:cd05901   93 IVKLRASDAGVYRCEV 108

Immunoglobulin variable (IgV)-like domain in complement receptor of the immunoglobulin superfamily (CRIg); The members here are composed of the immunoglobulin variable (IgV) region of the complement receptor of the immunoglobulin superfamily (CRIg). The N-terminal domain of CRIg (also known as Z39Ig and V-set and Ig domain-containing 4 (VSIG4) belongs to the IgV family of immunoglobulin-like domains while the C-terminal domain of CRIg belongs to the IgC family of immunoglobulin-like domains. Like all members of this family, the CRIg domain contains two beta-sheets: one composed of strands A', G, F, C, C' and C", and the other of strands B, E and D. The complement system is an important part of the innate immune system and is required for removal of pathogens from the bloodstream. After exposure to pathogens, the third component of the complement system, C3, is cleaved to C3b which, after recruitment of factor B, initiates formation of the alternative pathway convertases. CRIg, a complement receptor expressed on macrophages, binds to C3b and iC3b mediating phagocytosis of the particles. It is also a potent inhibitor of the alternative pathway convertases and a negative regulator of T cell activation. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, such as, T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, such as, butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  22 ITTPEEMIEKAKGETAyLPCkfTLSPE-DQGPLDIEWLISpadnQKVDQVIILY---SGDKIYDDYYpdlKGRVHFTSNd 97
Cdd:cd16089    3 LEGPESITGPWKGSVN-LPC--TYVPEeGYTQVLVKWLVQ----RDSDPVTIFLrdsSGDHIQQAKY---RGRLEVSKD- 71

                         90       100
                 ....*....|....*....|....*
gi 768020327  98 lKSGDASINVTNLQLSDIGTYQCKV 122
Cdd:cd16089   72 -TPGDVSLQLDTLEMDDRGHYTCQV 95

Immunoglobulin Variable region-containing chitin-binding proteins; an immunoglobulin V-set domain; The members here are composed of the immunoglobulin variable (IgV) region-containing chitin-binding proteins (VCBPs). VCBPs are secreted, immune-type molecules that have been identified in both amphioxus and sea squirt (Ciona intestinalis). VCBPs, which consist of a leader peptide, two tandem N-terminal immunoglobulin V-type domains and a single C-terminal chitin-binding domain, belong to a multigene family encoding secreted proteins. The VCBPs were identified first in the cephalochordate Branchiostoma floridae and show structural similarities with V-type domains of immunoglobulins and T cell receptors, suggesting that VCBPs represent a unique gut-associated form of innate immune proteins. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, such as, T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, such as, butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. This group belongs to the V-set of IgSF domains, having A, B, E and D strands in one beta-sheet and A', G, F, C, C' and C" in the other.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  34 GETAYLPCKFTLSPEDQGPLdIEWL--ISPADNQKV---DQVIILYSGDkiYDDYYPDLKGRVhfTSNDLKSgdASINVT 108
Cdd:cd20963   17 GNRVELPCSYTISPAAQPPT-ITWLkgISVDRAEVVfkgFKYWNETSSS--GEVYFGDYAGRA--SVASLTQ--PTLVLT 89

                         90
                 ....*....|....
gi 768020327 109 NLQLSDIGTYQCKV 122
Cdd:cd20963   90 DLKFDDWGRYWCRV 103

First immunoglobulin variable (IgV) domain of DNAX accessory molecule 1, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of DNAX accessory molecule 1 (DNAM-1, also known as CD226). DNAM-1 is a transmembrane protein having two Ig-like domains. It is an adhesion molecule which plays a part in tumor-directed cytotoxicity and adhesion in natural killer (NK) cells and T lymphocytes. It has been shown to regulate the NK cell killing of several tumor types, including myeloma cells and ovarian carcinoma cells. DNAM-1 interacts specifically with poliovirus receptor (PVR; CD155) and nectin -2 (CD211), other members of the Ig superfamily. DNAM-1 is expressed in most peripheral T cells, NK cells, monocytes and a subset of B lymphocytes.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|...
gi 768020327  85 PDLKGRVHFTSNDLKSGDASINVTNLQLSDIGTYQCKVKKAP-GVANKKIHLV 136
Cdd:cd05889   57 KPYAGRVYFLNSTMASNNMSLSFRNASEDDVGYYSCSLYTYPqGSWEKVIQVV 109

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 768020327  34 GETAYLPCKFTLSPEDQgpldIEWLiSPAdnqkvdqviilysGDKIYDDYYPDLKGR----VHFTSNDLksgdaSINVTN 109
Cdd:cd05717   11 GETLTLKCQVSLRDDSS----LQWL-NPN-------------GQTIYFNDKRALRDSryqlLNHSASEL-----SISVSN 67

                         90       100
                 ....*....|....*....|....*...
gi 768020327 110 LQLSDIGTYQCKVKKAPgVANKKIHLVV 137
Cdd:cd05717   68 VTLSDEGVYTCLHYTDP-VSTKKVTVTV 94