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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       3 KTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRV 82
Cdd:cd05770  1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                       90
               ....*....|....
3MA7_D      83 KHASMAEPKTVYWD 96
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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       3 KTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRV 82
Cdd:cd05770  1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                       90
               ....*....|....
3MA7_D      83 KHASMAEPKTVYWD 96
Cdd:cd05770 81 RHNTLSEPKIYKWD 94

Immunoglobulin C-Type;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
3MA7_D         20 PNILNCYVTQFHPPHIEIQMLKNGKKIP-KVEMSDMSFSKDWSFYILAHTEF---TPTETDTYACRVKHASMAEP 90
Cdd:smart00407  1 KATLVCLVSGFYPPDITVTWLRNGQEVTeGVSTTDPLKNSDGTYFLSSYLTVpasTWESGDVYTCQVTHEGLKEP 75

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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       3 KTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRV 82
Cdd:cd05770  1 STPKVQVYSRFPAENGKPNVLNCYVSGFHPPDIEIRLLKNGVKIEDVEQSDLSFSKDWTFYLLKYTEFTPTKGDEYACRV 80

                       90
               ....*....|....
3MA7_D      83 KHASMAEPKTVYWD 96
Cdd:cd05770 81 RHNTLSEPKIYKWD 94

Immunoglobulin C1-set domain;

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D         7 IQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTE---TDTYACRV 82
Cdd:pfam07654  1 VYVFPPSPEELGKPNTLTCLVTGFYPPDITVTWLKNGQEVTEgVKTTPPSPNSDWTYQLSSYLTVTPSDwesGDEYTCRV 80

                 ....*
3MA7_D        83 KHASM 87
Cdd:pfam07654 81 EHEGL 85

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain; 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 beta 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 has 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKI-PKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVK 83
Cdd:cd05766  4 PSVKVSPTKTGPLEHPNLLVCSVTGFYPAEIEVKWFRNGQEEtAGVVSTELIPNGDWTFQILVMLETTPRRGDVYTCQVE 83

                       90
               ....*....|...
3MA7_D      84 HASMAEPKTVYWD 96
Cdd:cd05766 84 HSSLQSPLTVDWR 96

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) DQ and related proteins; 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) DQ. MHC class II molecules are encoded by three different loci, HLA-DR, -DQ, and -DP, which are about 70% similar to each other. HLA-DQ (DQ) is a cell surface receptor protein found on antigen presenting cells. It is an alphabeta heterodimer of type MHC class II. The alpha and beta chains are encoded by two loci, HLA-DQA1 and HLA-DQB1, that are adjacent to each other on chromosome band 6p21.3. A person often produces two alpha-chain and two beta chain variants and thus 4 isoforms of DQ. Two autoimmune diseases in which HLA-DQ is involved are celiac disease and diabetes mellitus type 1. DQ is one of several antigens involved in rejection of organ transplants. DQ8 is a split antigen of the DQ3 broad antigen. 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       3 KTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIpKVEMSDMSF--SKDWSFYILAHTEFTPTETDTYAC 80
Cdd:cd21008  1 EVPEVTVFPKSPVTLGQPNTLICLVDNIFPPVINITWLSNGHSV-TEGVSETSFlsKSDHSFLKISYLTFLPSADDIYDC 79

                       90
               ....*....|....*.
3MA7_D      81 RVKHASMAEPKTVYWD 96
Cdd:cd21008 80 KVEHWGLDKPLLKHWE 95

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DP; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DP. HLA class II histocompatibility antigen, DP(W2) beta chain is a protein that in humans is encoded by the HLA-DPB1 gene. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. MHC class II molecules are encoded by three different loci, HLA-DR, -DQ, and -DP, which are about 70% similar to each other. HLA-DP is an alphabeta heterodimer cell-surface receptor. Each DP subunit (alpha-subunit, beta-subunit) is composed of a alpha-helical N-terminal domain, an IgG-like beta sheet, a membrane spanning domain, and a cytoplasmic domain. The alpha-helical domain forms the sides of the peptide binding groove. The beta sheet regions form the base of the binding groove and the bulk of the molecule as well as the inter-subunit (non-covalent) binding region. Individuals carrying the MHCII allele, HLA-DP2, are at risk for chronic beryllium disease (CBD), a debilitating inflammatory lung condition caused by the reaction of CD4 T cells to inhaled beryllium. 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
3MA7_D      20 PNILNCYVTQFHPPHIEIQMLKNGK-KIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVKHASMAEPKTVYW 95
Cdd:cd21003 19 HNLLVCHVTDFYPGNIQVRWFLNGQeETAGVVSTNLIHNGDWTFQILVMLEMTPQQGDVYTCQVEHPSLDSPVTVEW 95

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DR; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DR. HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. HLA-DR is also involved in several autoimmune conditions, disease susceptibility, and disease resistance including seronegative-rheumatoid arthritis, penicillamine-induced myasthenia, schizophrenia, Goodpasture syndrome, systemic lupus erythematosus, Alzheimers, tuberculoid leprosy, and Hashimoto's thyroiditis. HLA-DR molecules are upregulated in response to signaling. HLA-DR is an alphabeta heterodimer cell surface receptor, each subunit of which contains two extracellular domains, a membrane-spanning domain, and a cytoplasmic tail. Both alpha and beta chains are anchored in the membrane. The DR beta chain is encoded by 4 loci, however no more than 3 functional loci are present in a single individual, and no more than two on a single chromosome. Sometimes an individual may only possess 2 copies of the same locus, DRB1*. The HLA-DRB1 locus is ubiquitous and encodes a very large number of functionally variable gene products (HLA-DR1 to HLA-DR17). The HLA-DRB3 locus encodes the HLA-DR52 specificity, is moderately variable and is variably associated with certain HLA-DRB1 types. The HLA-DRB4 locus encodes the HLA-DR53 specificity, has some variation, and is associated with certain HLA-DRB1 types. The HLA-DRB5 locus encodes the HLA-DR51 specificity, which is typically invariable, and is linked to the HLA-DR2 types. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVYsrhpPENGKP----NILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYA 79
Cdd:cd21000  4 PKVTVY----PAKTQPlqhhNLLVCSVNGFYPGSIEVRWFRNGQEEKAgVVSTGLIQNGDWTFQTLVMLETVPRSGEVYT 79

                       90
               ....*....|....*.
3MA7_D      80 CRVKHASMAEPKTVYW 95
Cdd:cd21000 80 CQVEHPSVTSPLTVEW 95

Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DQ and I-A; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of human histocompatibility antigen (HLA) DQ and mouse I-A. Three genetically distinct isotypes of class II MHC molecules are found in humans (HLA-DR, HLA-DQ, and HLA-DP), and two in mice (I-E and I-A). I-A and I-E have the same basic features insofar as peptide loading and presentation, they differ in that each interacts with distinctly different sets of peptides, and in the incidence of deletion of their genes. A structural understanding of the similarities and differences between I-A and I-E may help with understanding their roles in peptide presentation and T cell activation. Mouse I-Ag7 has a genetic susceptibility to autoimmune diabetes due to its small, uncharged amino acid residue at position 57 of their beta chain which results in the absence of a salt bridge between beta 57 and Arg alpha 76, which is adjacent to the P9 pocket of the peptide-binding groove. Human HLA-DR, -DQ, and -DP are about 70% similar to each other. HLA-DQ (DQ) is a cell surface receptor protein found on antigen presenting cells. It is an alphabeta heterodimer of type MHC class II. The alpha and beta chains are encoded by two loci, HLA-DQA1 and HLA-DQB1, that are adjacent to each other on chromosome band 6p21.3. A person often produces two alpha-chain and two beta chain variants and thus 4 isoforms of DQ. HLA-DQ is involved in the autoimmune diseases celiac disease and diabetes mellitus type. DQ is one of several antigens involved in rejection of organ transplants. DQ2 is encoded by the HLA-DQB1*02 allele group. DQ6 is encoded by the HLA-DQB1*06 allele group. DQ2 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, nicknamed DQ2.2 and DQ2.5, are also encoded by the DQA1*0201 and DQA1*0501 genes, respectively. DQ6 beta-chains combine with alpha-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. For DQ6, however, cis-isoform pairing only occurs with DQ1 alpha-chains. There are many haplotypes of DQ6. Susceptibility to Leptospirosis infection was found associated with undifferentiated DQ6. DQ8 is determined by the antibody recognition of beta8 and this generally detects the gene product of DQB1*0302. DQ8 is commonly linked to autoimmune disease in the human population. DQ8 is the second most predominant isoform linked to celiac disease and the DQ most linked to Type 1 diabetes. DQ8 increases the risk for rheumatoid arthritis and is linked to the primary risk locus for RA, HLA-DR4. DR4 also plays an important role in Type 1 diabetes. DQ8 is a split antigen of the DQ3 broad antigen. MHC class II molecules play a key role in the initiation of the antigen-specific immune response. They are expressed constitutively on the cell surface of professional antigen-presenting cells (APCs), including B-lymphocytes, monocytes, and macrophages in both humans and mice, and induced in nonprofessional APCs, such as keratinocyctes; they are expressed on the surface of activated human T cells and on T cells from other species. 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, and 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
3MA7_D      21 NILNCYVTQFHPPHIEIQMLKNGKK-IPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVKHASMAEPKTVYW 95
Cdd:cd21001 20 NLLVCSVTDFYPGQIKVRWFRNDQEeTAGVVSTPLIRNGDWTFQILVMLEMTPQRGDVYTCHVEHPSLQSPITVEW 95

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) I-E; 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) I-E. 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPKvEMSDMSF--SKDWSFYILAHTEFTPTETDTYACRV 82
Cdd:cd21005  3 PEVTVLSRSPVNLGEPNILICFIDKFSPPVVNVTWLRNGRPVTE-GVSETVFlpRDDHLFRKFHYLTFLPSTDDFYDCEV 81

                       90
               ....*....|....
3MA7_D      83 KHASMAEPKTVYWD 96
Cdd:cd21005 82 DHWGLEEPLRKHWE 95

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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       4 TPQIQVYSRHPPENGKPNILnCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMSF-SKDWSFYILAHTEFTPTETD---TYA 79
Cdd:cd00098  1 TVTLLPPSPEEKGGGKVTLV-CLVSGFYPKDITVTWLKNGVPLTSGVSTSSPVePNDGTYSVTSSLTVPPSDWDegaTYT 79

                       90
               ....*....|....*.
3MA7_D      80 CRVKHASMAEPKTVYW 95
Cdd:cd00098 80 CVVTHESLKSPLSKTW 95

Class I major histocompatibility complex (MHC) alpha chain, alpha3 immunoglobulin domain; 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 I alpha chain. 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        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVYSRHPPENGKPniLNCYVTQFHPPHIEIQMLKNGKKI-PKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVK 83
Cdd:cd07698  3 PKVHVTHHPRSDGEST--LRCWALGFYPAEITLTWQRDGEDQtQDMELVETRPNGDGTFQKWAAVVVPSGEEQRYTCHVQ 80

                       90
               ....*....|..
3MA7_D      84 HASMAEPKTVYW 95
Cdd:cd07698 81 HEGLPEPLTLRW 92

Immunoglobulin domain of Zn-alpha2-glycoprotein (ZAG); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Zn-alpha2-glycoprotein (ZAG). ZAG is a soluble protein that is present in serum and other body fluids. ZAG stimulates lipid degradation in adipocytes and causes the extensive fat losses associated with some advanced cancers. The 2.8 angstrom crystal structure of ZAG resembles a class I major histocompatibility complex (MHC) heavy chain, but ZAG does not bind the class I light chain beta-2-microglobulin. The ZAG structure includes a large groove analogous to class I MHC peptide binding grooves. Instead of a peptide, the ZAG groove contains a nonpeptidic compound that may be implicated in lipid catabolism under normal or pathological conditions. IgC_MHC_I_alpha3; Immunoglobulin (Ig) domain of major histocompatibility complex (MHC) class I alpha chain. 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        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       2 QKTPQIQVYSRHPPenGKPNILNCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACR 81
Cdd:cd21010  2 QDPPSVSVTSHVAP--GKNRTLKCLAYDFYPRGISLHWTRAGKVQESESGGDVLPSGNGTYQSWVVVEVPPQDRAPYSCH 79

                       90
               ....*....|....
3MA7_D      82 VKHASMAEPKTVYW 95
Cdd:cd21010 80 VEHSSLAQPLTVPW 93

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of T10, T22, and similar proteins; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of the murine H-2T-encoded T10, T22, and similar proteins. T10 and T22 are highly related nonclassical major histocompatibility complex (MHC) class Ib proteins that bind to certain gammadelta T cell receptors (TCRs) in the absence of other components. Classical MHC class I (class Ia) molecules participate in immune responses by presenting peptide antigens to cytolytic alpha beta T cells. Many nonclassical MHC class I (class Ib) molecules have distinct antigen-binding capabilities, suggesting that they have evolved for specific tasks that are distinct from those of MHC class Ia. Members of the IgC 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D      11 SRHPPENGKPNiLNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVKHASMAE 89
Cdd:cd21016 11 TRHPRPEGDVT-LRCWALGFYPADITLTWQKDGEELTQdMEFVETRPAGDGTFQKWAAVVVPLGKEQSYTCHVYHEGLPE 89

               ....*..
3MA7_D      90 PKTVYWD 96
Cdd:cd21016 90 PLTLRWE 96

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1b; member of the C1-set of Ig superfamily (IgSF) domains; The non-classical mouse MHC class I (MHC-I) molecule Qa-1b is a non-polymorphic MHC molecule with an important function in innate immunity. It binds and presents signal peptides of classical MHC-I molecules at the cell surface and, as such, act as an indirect sensor for the normal expression of MHC-I molecules. This signal peptide dominantly accommodated in the groove of Qa-1b is called Qdm, for Qa-1 determinant modifier, and its amino acid sequence AMAPRTLLL is highly conserved among mammalian species. The Qdm/Qa-1b complex serves as a ligand for the germ-line encoded heterodimeric CD94/NKG2A receptors expressed on natural killer (NK) cells and activated CD8+ T cells and transduces inhibitory signals to these lymphocytes. Thus, upon binding, Qa-1b signals NK cells not to engage in cell lysis. The molecular basis of Qa-1b function is unclear.

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               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       2 QKTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYAC 80
Cdd:cd21820  1 QRSDPPKAHVTHHPRSEDEVTLRCWALGFYPADITLTWQLNGEELTQdMELVETRPAGDGTFQKWAAVVVPLGKEQYYTC 80

                       90
               ....*....|....*.
3MA7_D      81 RVKHASMAEPKTVYWD 96
Cdd:cd21820 81 HVYHEGLPEPLTLRWE 96

H-2 class I histocompatibility complex TLA (thymus leukemia antigen); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the major histocompatibility complex (MHC) H-2 class I histocompatibility complex TLA (thymus leukemia antigen). The murine MHC class I histocompatibility TLA (Thymus leukemia antigen), which is encoded in the T region by T3 and T18 genes, is expressed mainly by intestinal epithelial cells and thymocytes. The murine TLAs are class I, beta-2-microglobulin-associated glycoproteins. The TLA function is not defined by antigen presentation, but rather by its relatively high affinity binding to CD8-alpha-alpha compared with CD8-alpha-beta. The existence of a human homolog for murine TLA remains unresolved. This group is a member of the C1-set Ig domains, which 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVySRHPPENGKPNiLNCYVTQFHPPHIEIQMLKNGKK-IPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVK 83
Cdd:cd21012  6 PKTHV-THHPRPEGYVT-LRCWALGFYPAHITLTWQLNGEElIQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVY 83

                       90
               ....*....|..
3MA7_D      84 HASMAEPKTVYW 95
Cdd:cd21012 84 HEGLPEPLTLRW 95

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of HLA-Cw3 and HLA-Cw4. HLA-C belongs to the MHC class I heavy chain receptors. The C receptor is a heterodimer consisting of a HLA-C mature gene product and beta-2-microglobulin. The mature C chain is anchored in the membrane. MHC Class I molecules, like HLA-C, are expressed in nearly all cells, and present small peptides to the immune system which surveys for non-self peptides. HLA-C is a locus on chromosome 6, which encodes for a large number of HLA-C alleles that are Class-I MHC receptors. Class Ib histocompatibility leukocyte antigens (HLA)-Cw3 and (HLA)-Cw4 are ligands for the natural killer (NK) cell inhibitory receptors KIR2DL2 and KIR2DL1, respectively. HLA-Cw3 and related alleles (HLA-Cw1, -Cw7, and -Cw8) contain Ser77 and Asn80 and interact with KIR that are reactive with the GL183 antibody Class I MHC proteins bind antigenic peptide fragments and present them to CD8+ T lymphocytes. HLA-Cw4 and related alleles (HLA-Cw2, -Cw5, and -Cw6) have Asn77 and Lys80 and are recognized by KIR reactive with the EB6 15 or HP-3E4 16 antibody. Members of the IgC 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
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       2 QKTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGK-KIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYAC 80
Cdd:cd21025  1 QRAEHPKTHVTHHPVSDHEATLRCWALGFYPAEITLTWQWDGEdQTQDTELVETRPAGDGTFQKWAAVVVPSGEEQRYTC 80

                       90
               ....*....|....*
3MA7_D      81 RVKHASMAEPKTVYW 95
Cdd:cd21025 81 HVQHEGLPEPLTLRW 95

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-2; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ib major histocompatibility complex (MHC) immunoglobulin domain of QA-2. Qa-2 is a nonclassical MHC Ib antigen, which has been implicated in both innate and adaptive immune responses, as well as embryonic development. Qa-2 has an unusual peptide binding specificity in that it requires two dominant C-terminal anchor residues and is capable of associating with a substantially more diverse array of peptide sequences than other nonclassical MHC. 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.

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               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       8 QVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVKHAS 86
Cdd:cd21014  6 KAHVTHHPRSYGAVTLRCWALGFYPADITLTWQLNGEELTQdMELVETRPAGDGTFQKWASVVVPLGKEQNYTCHVNHEG 85

               ....*....
3MA7_D      87 MAEPKTVYW 95
Cdd:cd21014 86 LPEPLTLRW 94

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H2-Dd; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H2-Dd. Mouse MHC is composed of 11 subclasses. It includes the classical MHC class I (MHC-Ia) that comprises H-2D, H-2K and H-2L subclasses, the non-classical MHC class I (MHCIb) that comprises H-2Q, H-2M and H-2T subclasses, the classical MHC class II (MHC-IIa) that includes H-2A(I-A) and H-2E(I-E) subclasses, and the non-classical MHC class II (MHC-IIb) comprises H-2M and H-2O. H-2K, H-2D, and H-2L are 80 to 90% homologous at the amino acid level yet appear to be involved in different recognition reactions and are differentially expressed on lymphoid cells. 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        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       5 PQIQVYSRHPPENGKpnILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVK 83
Cdd:cd21020  6 PKAHVTHHRRPEGDV--TLRCWALGFYPADITLTWQLNGEELTQeMELVETRPAGDGTFQKWASVVVPLGKEQKYTCHVE 83

                       90
               ....*....|..
3MA7_D      84 HASMAEPKTVYW 95
Cdd:cd21020 84 HEGLPEPLTLRW 95

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins; member of the C1-set of Ig superfamily (IgSF) domains; Class Ib major histocompatibility complex (MHC) immunoglobulin domain of Qa-1 and similar proteins. Qa-1 presents hydrophobic peptides including Qdm derived from the leader sequence of classical MHC I molecules for immune surveillance by NK cells. Qa-1 bound peptides derived from the TCR Vbeta8.2 of activated T cells also activates CD8+ regulatory T cells to control autoimmunity and maintain self-tolerance. Four allotypes of Qa-1 (Qa-1a-d) are expressed that are highly conserved in sequence but have several variations that could affect peptide binding to Qa-1 or TCR recognition. 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        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D      13 HPPENGKPNILNCYVTQFHPPHIEIQMLKNGKKIPK-VEMSDMSFSKDWSFYILAHTEFTPTETDTYACRVKHASMAEPK 91
Cdd:cd21013 11 HHPRSEGYVTLRCWALGFYPADITLTWQLNGEELTQdMEFVETRPAGDGTFQKWASVVVPLGKEQKYTCHVEHEGLPEPL 90

               ....*
3MA7_D      92 TVYWD 96
Cdd:cd21013 91 TLRWE 95

CH2 domain (second constant Ig domain of the heavy chain) in immunoglobulin mu chain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin constant domain (IgC) of mu heavy chains. This domain is found on the Fc fragment. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda; each is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns.

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               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D      13 HPP-----ENGKPNILNCYVTQFHPPHIEIQMLKNGKKIP---------KVEMSDMSFS---------KDWsfyiLAHTE 69
Cdd:cd16093  7 HAPsreefLGNRTATFVCLATGFSPKTISFKWLRNGKEVTsstgavveePKEDGKTLYSatsfltiteSEW----KSQTE 82

                       90       100
               ....*....|....*....|....
3MA7_D      70 FTptetdtyaCRVKHASMAEPKTV 93
Cdd:cd16093 83 FT--------CEFKHKGEIVEKNA 98

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) A; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) A. The classical class I molecules (HLA-A, -B, and -C) are responsible for the presentation of endogenous antigen to CD8+ T cells. The receptor is a heterodimer, and is composed of a heavy alpha chain and smaller beta chain. The alpha chain is encoded by a variant HLA-A gene, and the beta chain (beta-2-microglobulin) is an invariant beta-2-microglobulin molecule. The beta-2-microglobulin protein is coded for by a separate region of the human genome. HLA-A2 is associated with spontaneous abortions, HIV, and Hodgkin lymphoma. 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.

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               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D       2 QKTPQIQVYSRHPPENGKPNILNCYVTQFHPPHIEIQMLKNGK-KIPKVEMSDMSFSKDWSFYILAHTEFTPTETDTYAC 80
Cdd:cd21027  1 QRTDAPKTHMTHHAVSDHEATLRCWALSFYPAEITLTWQRDGEdQTQDTELVETRPAGDGTFQKWAAVVVPSGQEQRYTC 80

                       90
               ....*....|....*
3MA7_D      81 RVKHASMAEPKTVYW 95
Cdd:cd21027 81 HVQHEGLPKPLTLRW 95

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin delta chain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin constant-1 set domain of delta chains. It belongs to a family composed of the first immunoglobulin constant-1 set domain of alpha, delta, epsilon, gamma, and mu heavy chains. This domain is found on the Fab antigen-binding fragment. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda; each is composed of a constant domain and a variable domain. There are five types of heavy chains: alpha, delta, epsilon, gamma, and mu, all consisting of a variable domain (VH) with three (alpha, delta and gamma) or four (epsilon and mu) constant domains (CH1 to CH4). Ig molecules are modular proteins, in which the variable and constant domains have clear, conserved sequence patterns. This group belongs to the C1-set of IgSF domains, which are classical Ig-like domains resembling the antibody constant domain. C1-set domains are found almost exclusively in molecules involved in the immune system, such as in immunoglobulin light and heavy chains, in the major histocompatibility complex (MHC) class I and II complex molecules, and in various T-cell receptors.

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               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
3MA7_D      12 RHPPENgKPNILNCYVTQFHPPHIEIQMLKNGKKIPKVEMSDMsfSKDWSFYILAHTEFTPTE---TDTYACRVKHASMA 88
Cdd:cd16092 12 RHPKDN-SPVVLACLITGYHPTSVTVTWYMGTQSQPQRTFPEI--QRRDSYYMTSSQLSTPLQqwrQGEYKCVVQHTASK 88

               ....*.
3MA7_D      89 EPKTVY 94
Cdd:cd16092 89 SKKEIF 94