Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  21 SPPVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPDCKQTDPSFQHNWKYYTTKSTHVHIDKGDKVECVV 100
Cdd:cd05770    1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                         90
                 ....*....|....
gi 147904734 101 SHNG-NPSKKYRLD 113
Cdd:cd05770   81 RHNTlSEPKIYKWD 94

Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  21 SPPVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPDCKQTDPSFQHNWKYYTTKSTHVHIDKGDKVECVV 100
Cdd:cd05770    1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                         90
                 ....*....|....
gi 147904734 101 SHNG-NPSKKYRLD 113
Cdd:cd05770   81 RHNTlSEPKIYKWD 94

Immunoglobulin C-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 147904734    38 TNEVICYVYNYHPPRLEMRLEKNGVEIP-DCKQTDPSFQHNWKYYTTKSTHVHID---KGDKVECVVSHNGNPS 107
Cdd:smart00407   1 KATLVCLVSGFYPPDITVTWLRNGQEVTeGVSTTDPLKNSDGTYFLSSYLTVPAStweSGDVYTCQVTHEGLKE 74

Class I major histocompatibility complex (MHC) beta-2-microglobulin; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin-like domain in beta-2-microglobulin (beta2m). Beta2m is the non-covalently bound light chain of the human class I major histocompatibility complex (MHC-I). Beta2m is structured as a beta-sandwich domain composed of two facing beta-sheets (four stranded and three stranded), that is typical of the C-type immunoglobulin superfamily. This structure is stabilized by an intramolecular disulfide bridge connecting two Cys residues in the facing beta-sheets. In vivo, MHC-I continuously exposes beta2m on the cell surface, where it may be released to plasmatic fluids, transported to the kidneys, degraded, and finally excreted.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  21 SPPVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPDCKQTDPSFQHNWKYYTTKSTHVHIDKGDKVECVV 100
Cdd:cd05770    1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                         90
                 ....*....|....
gi 147904734 101 SHNG-NPSKKYRLD 113
Cdd:cd05770   81 RHNTlSEPKIYKWD 94

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of the major histocompatibility complex (MHC) class II alpha chain. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are also expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  22 PPVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPD-CKQTDPSFQHNWKYYTTKSTHVHIDKGDKVECVV 100
Cdd:cd05767    2 PPEVTVFPKSPVELGEPNTLICFVDNFFPPVINVTWLRNGQPVTDgVSETVFLPREDHSFRKFSYLPFTPSEGDIYDCRV 81

                 ....
gi 147904734 101 SHNG 104
Cdd:cd05767   82 EHWG 85

Immunoglobulin Constant-1 (C1)-set domain; The members here are composed of C1-set domains, classical Ig-like domains resembling the antibody constant domain. Members of the IgC1 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, while the IgC domain is involved in oligomerization and molecular interactions. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other strands by G, F, C, and C'.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  29 TAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPDCKQTDPSFQHNWKYYTTKS----THVHIDKGDKVECVVSHNG 104
Cdd:cd00098    7 PSPEEKGGGKVTLVCLVSGFYPKDITVTWLKNGVPLTSGVSTSSPVEPNDGTYSVTSsltvPPSDWDEGATYTCVVTHES 86

                 ....
gi 147904734 105 NPSK 108
Cdd:cd00098   87 LKSP 90

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) DM; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class II alpha chain of histocompatibility antigen (HLA) DM. Human HLA-DM, also known as H2-M in mice, plays a critical role in antigen presentation to CD4 T cells by catalyzing the exchange of peptides bound to MHC class II molecules. MHC class II molecules play a key role in the initiation of the antigen-specific immune reponse. These molecules have been shown to be expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice. The expression of these molecules has been shown to be induced in nonprofessional APCs such as keratinocyctes, and they are expressed on the surface of activated human T cells and on T cells from other species. The MHC II molecules present antigenic peptides to CD4(+) T-lymphocytes. These peptides derive mostly from proteolytic processing via the endocytic pathway, of antigens internalized by the APC. These peptides bind to the MHC class II molecules in the endosome before they are transported to the cell surface. MHC class II molecules are heterodimers, comprised of two similarly-sized membrane-spanning chains, alpha and beta. Each chain had two globular domains (N- and C-terminal), and a membrane-anchoring transmembrane segment. The two chains form a compact four-domain structure. The peptide-binding site is a cleft in the structure.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 147904734  23 PVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEIPDCKQTDPSFQHNWKYYTTKSTHVHIDKGDKVECVVSH 102
Cdd:cd21009    3 PIAEVFTLKPLEFGKPNTLVCFVSNLFPPMLTVNWQLHSVPVEGFGPTFVSAVDGLSFQAFSYLNFTPEPSDIFSCIVTH 82

HLA class II histocompatibility antigen DO alpha; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the nonclassical MHC class II (MHCII) protein, HLA-DO, which binds HLA-DM and influences the repertoire of peptides presented by MHCII proteins. In complex with HLA-DM, HLA-DO adopts a classical MHCII structure, with alterations near the a subunit's 310 helix. HLA-DO binds to HLA-DM at the same sites implicated in MHCII interaction, and kinetic analysis showed that HLA-DO acts as a competitive inhibitor by acting as a substrate mimic. Though more remains to be elucidated about the function of HLA-DO, its unique distribution in the mammalian body namely, the exclusive expression of HLA-DO in B cells, thymic medullary epithelial cells, and dendritic cells indicate that it may be of physiological importance and has inspired further research. Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. Class I molecules consist of a transmembrane alpha chain and a small chain called the beta-2-microglobulin. The alpha chain contains three extracellular domains, two of which fold together to form the peptide-binding cleft (alpha1 and alpha2), and one which has an Ig fold (alpha3). Peptide binding to class I molecules occurs in the endoplasmic reticulum (ER) and involves both chaperones and dedicated factors to assist in peptide loading. Class I MHC molecules are expressed on most nucleated cells.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|...
gi 147904734  22 PPVVKVYTAEPVDFGKTNEVICYVYNYHPPRLEMRLEKNGVEI 64
Cdd:cd21004    2 PPRVTVLPKSRVELGQPNILICIVDNIFPPVINITWLRNGQTV 44