Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen H; 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 human leukocyte antigen H (HLA-H). HLA-H (also known as hereditary hemochromatosis protein; HFE) is a major histocompatibility complex (MHC) class I-like protein that is mutated in Hereditary Hemochromatosis. HFE is a protein of 343 amino acids that includes a signal peptide, an extracellular transferrin receptor-binding region (a1 and a2), an immunoglobulin-like domain (a3), a transmembrane region, and a short cytoplasmic tail. HFE binds beta-2-microglobulin to form a heterodimer expressed at the cell surface. It binds transferrin receptor (TFRC) in its extracellular alpha1-alpha2 domain. HFE plays an important part in the regulation of hepcidin expression in response to iron overload and the liver is important in the pathophysiology of HFE-associated hemochromatosis. Nine HFE splicing variants have been reported with transcripts lacking exon 2 or exon 3, or exons 2-3, 2-4, or 2-5. Diverse mutations involving HFE introns and exons discovered in persons with hemochromatosis or their family members cause or probably cause high iron phenotypes. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 204 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 283
Cdd:cd21021     1 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 80

                          90
                  ....*....|....
gi 1847913971 284 VEHPGLDQPLIVIW 297
Cdd:cd21021    81 VEHPGLDQPLIVIW 94

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen H; 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 human leukocyte antigen H (HLA-H). HLA-H (also known as hereditary hemochromatosis protein; HFE) is a major histocompatibility complex (MHC) class I-like protein that is mutated in Hereditary Hemochromatosis. HFE is a protein of 343 amino acids that includes a signal peptide, an extracellular transferrin receptor-binding region (a1 and a2), an immunoglobulin-like domain (a3), a transmembrane region, and a short cytoplasmic tail. HFE binds beta-2-microglobulin to form a heterodimer expressed at the cell surface. It binds transferrin receptor (TFRC) in its extracellular alpha1-alpha2 domain. HFE plays an important part in the regulation of hepcidin expression in response to iron overload and the liver is important in the pathophysiology of HFE-associated hemochromatosis. Nine HFE splicing variants have been reported with transcripts lacking exon 2 or exon 3, or exons 2-3, 2-4, or 2-5. Diverse mutations involving HFE introns and exons discovered in persons with hemochromatosis or their family members cause or probably cause high iron phenotypes. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 204 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 283
Cdd:cd21021     1 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 80

                          90
                  ....*....|....
gi 1847913971 284 VEHPGLDQPLIVIW 297
Cdd:cd21021    81 VEHPGLDQPLIVIW 94

Immunoglobulin C-Type;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1847913971  222 TLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVP---PGEEQRYTCQVEHPGLDQP 292
Cdd:smart00407   3 TLVCLVSGFYPPDITVTWLRNGQEV-TEGVSTTDPLKNSDGTYFLSSYLTVPastWESGDVYTCQVTHEGLKEP 75

Class Ib major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen H; 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 human leukocyte antigen H (HLA-H). HLA-H (also known as hereditary hemochromatosis protein; HFE) is a major histocompatibility complex (MHC) class I-like protein that is mutated in Hereditary Hemochromatosis. HFE is a protein of 343 amino acids that includes a signal peptide, an extracellular transferrin receptor-binding region (a1 and a2), an immunoglobulin-like domain (a3), a transmembrane region, and a short cytoplasmic tail. HFE binds beta-2-microglobulin to form a heterodimer expressed at the cell surface. It binds transferrin receptor (TFRC) in its extracellular alpha1-alpha2 domain. HFE plays an important part in the regulation of hepcidin expression in response to iron overload and the liver is important in the pathophysiology of HFE-associated hemochromatosis. Nine HFE splicing variants have been reported with transcripts lacking exon 2 or exon 3, or exons 2-3, 2-4, or 2-5. Diverse mutations involving HFE introns and exons discovered in persons with hemochromatosis or their family members cause or probably cause high iron phenotypes. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 204 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 283
Cdd:cd21021     1 QQVPPLVKVTHHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 80

                          90
                  ....*....|....
gi 1847913971 284 VEHPGLDQPLIVIW 297
Cdd:cd21021    81 VEHPGLDQPLIVIW 94

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 206 VPPLVKVTHHVTSS-VTTLRCRALNYYPQNITMKWLKDKQPMDAKEfEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQV 284
Cdd:cd07698     1 DPPKVHVTHHPRSDgESTLRCWALGFYPAEITLTWQRDGEDQTQDM-ELVETRPNGDGTFQKWAAVVVPSGEEQRYTCHV 79

                          90
                  ....*....|...
gi 1847913971 285 EHPGLDQPLIVIW 297
Cdd:cd07698    80 QHEGLPEPLTLRW 92

Immunoglobulin domain of Cluster of Differentiation (CD) 1; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of Cluster of Differentiation (CD) 1. CD1 family of transmembrane glycoproteins, are structurally related to the major histocompatibility complex (MHC) proteins and form heterodimers with beta-2-microglobulin. They mediate the presentation of primarily lipid and glycolipid antigens of self or microbial origin to T cells. The human genome contains five CD1 family genes (CD1a, CD1b, CD1c, CD1d, and CD1e) organized in a cluster on chromosome 1. The CD1 family members are thought to differ in their cellular localization and specificity for particular lipid ligands. CD1a localizes to the plasma membrane and to recycling vesicles of the early endocytic system. Alternative splicing results in multiple transcript variants. 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. C1-set Ig domains 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 1847913971 206 VPPLVKVTHH--VTSSVTTLRCRALNYYPQNITMKWLKDKQPMDaKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 283
Cdd:cd21029     1 VKPRVRLSSRpsPGDGHLQLSCHVTGFYPRPIEVTWLRDGQEQM-DGTQSGGILPNHDGTYQLRKTLDIAPGEGAGYSCR 79

                          90
                  ....*....|....
gi 1847913971 284 VEHPGLDQPLIVIW 297
Cdd:cd21029    80 VDHSSLKQDLIVYW 93

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) B and similar proteins; 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) B and similar proteins. 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-B 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. Human leukocyte antigen (HLA) B*3501 (B35) is a common human allele involved in mediating protective immunity against HIV. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 207 PPLVKVTHH-VTSSVTTLRCRALNYYPQNITMKWLKDKQPmDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVE 285
Cdd:cd21026     5 PPKTHVTHHpISDHEATLRCWALGFYPAEITLTWQRDGED-QTQDTELVETRPAGDRTFQKWAAVVVPSGEEQRYTCHVQ 83

                          90
                  ....*....|....
gi 1847913971 286 HPGLDQPLIVIWEP 299
Cdd:cd21026    84 HEGLPKPLTLRWEP 97

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.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 207 PPLVKVTHHVTSS-VTTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVE 285
Cdd:cd21820     5 PPKAHVTHHPRSEdEVTLRCWALGFYPADITLTWQLNGEEL-TQDMELVETRPAGDGTFQKWAAVVVPLGKEQYYTCHVY 83

                          90
                  ....*....|....
gi 1847913971 286 HPGLDQPLIVIWEP 299
Cdd:cd21820    84 HEGLPEPLTLRWEP 97

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of MIC-A and MIC-B; 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 MIC-A and MIC-B. MIC-A and MIC-B are homologs that serve as stress-inducible antigens on epithelial and epithelially derived cells. Both serve as ligands for the widely expressed activating immunoreceptor NKG2D, a C-type lectin-like activating immunoreceptor. MIC-B is very similar in structure to MIC-A and likely interacts with NKG2D in an analogous manner. The interdomain flexibility observed in the MIC-A structures, a feature unique to MIC proteins among MHC class I proteins and homologs, is also displayed by MIC-B, with an interdomain relationship intermediate between the two examples of MIC-A structures. Mapping sequence variations onto the structures of MIC-A and MIC-B reveals patterns completely distinct from those displayed by classical MHC class I proteins, with a number of substitutions falling on positions likely to affect interactions with NKG2D, but with other positions lying distant from the NKG2D binding sites or buried within the core of the proteins. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 204 QQVPPLVKVT-HHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTC 282
Cdd:cd21017     1 RTVPPMVNVTrSEASEGNITVTCRASGFYPWNITLSWRQDGVSLSHDTQQWGDVLPDGNGTYQTWVATRICQGEEQRFTC 80

                  ....*.
gi 1847913971 283 QVEHPG 288
Cdd:cd21017    81 YMEHSG 86

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 208 PLVKVTHH-VTSSVTTLRCRALNYYPQNITMKWLKDKQPmDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEH 286
Cdd:cd21025     6 PKTHVTHHpVSDHEATLRCWALGFYPAEITLTWQWDGED-QTQDTELVETRPAGDGTFQKWAAVVVPSGEEQRYTCHVQH 84

                          90
                  ....*....|..
gi 1847913971 287 PGLDQPLIVIWE 298
Cdd:cd21025    85 EGLPEPLTLRWE 96

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 207 PPLVKVTHHV-TSSVTTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVE 285
Cdd:cd21016     5 PPKAHVTRHPrPEGDVTLRCWALGFYPADITLTWQKDGEEL-TQDMEFVETRPAGDGTFQKWAAVVVPLGKEQSYTCHVY 83

                          90
                  ....*....|....
gi 1847913971 286 HPGLDQPLIVIWEP 299
Cdd:cd21016    84 HEGLPEPLTLRWEP 97

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of human leukocyte antigen (HLA) H2Db and H2Ld; 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) H2Db and H2Ld. H-2Ld complexed with peptide QL9 (or p2Ca) and complexed with influenza virus peptide NP366-374 (ASNEN-METM), respectively are high-affinity alloantigens for the 2C T cell receptor (TCR). The a1-a2 super domains of H-2Ld, H-2Db, and H-2Kb closely superimpose. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 208 PLVKVTHHVTSS-VTTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEH 286
Cdd:cd21018     6 PKAHVTHHPRSKgEVTLRCWALGFYPADITLTWQLNGEEL-TQDMELVETRPAGDGTFQKWASVVVPLGKEQNYTCRVYH 84

                          90
                  ....*....|.
gi 1847913971 287 PGLDQPLIVIW 297
Cdd:cd21018    85 EGLPEPLTLRW 95

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 207 PPLVKVTHHV-TSSVTTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVE 285
Cdd:cd21012     5 PPKTHVTHHPrPEGYVTLRCWALGFYPAHITLTWQLNGEEL-IQDTELVETRPAGDGTFQKWAAVVVPSGEEQKYTCHVY 83

                          90
                  ....*....|..
gi 1847913971 286 HPGLDQPLIVIW 297
Cdd:cd21012    84 HEGLPEPLTLRW 95

Class Ia major histocompatibility complex (MHC) immunoglobulin domain of H-2Kb; 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 H-2Kb. H-2Kb is an alloantigen for the 2C T cell receptor (TCR). H-2Kb forms a complex with beta-2-microglobulin, and a peptide, including VSV-8 (RGYVYNGL), SEV-9 (FAPGNYPAL), and OVA-8 (SIINFEKL). Comparison of the OVA-8, VSV-8, and SEV-9 complexes with H-2Kb indicates that four side chains (Lys-66, Glu-152, Arg-155, and Trp-167) adopt peptide-specific conformations. H-2Kb paralogs include H-2Db, H-2Kbml and H-2KbI1s. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 208 PLVKVTHHV-TSSVTTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEH 286
Cdd:cd21019     5 PKAHVTHHSrPEDKVTLRCWALGFYPADITLTWQLNGEEL-IQDMELVETRPAGDGTFQKWASVVVPLGKEQYYTCHVYH 83

                          90
                  ....*....|.
gi 1847913971 287 PGLDQPLIVIW 297
Cdd:cd21019    84 QGLPEPLTLRW 94

Class II major histocompatibility complex (MHC) beta 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 Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) DM. Human HLA-DM plays a critical role in antigen presentation to CD4 T cells by catalyzing the exchange of peptides bound to MHC class II molecules. Type 1 diabetes is correlated with DM activation and it is also implicated in viral infections such as herpes simplex virus, celiac disease, multiple sclerosis, other autoimmune diseases, and leukemia. 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 1847913971 205 QVPPLVKV---THHVTSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYT 281
Cdd:cd21002     1 RRPPSVRVaptTPFNTREPVMLACHVWGFYPADVTITWLKNGDPVAPHSSAPKTAQPNGDWTYQTQVTLAVTPSPGDTYT 80

                          90
                  ....*....|....*.
gi 1847913971 282 CQVEHPGLDQPLIVIW 297
Cdd:cd21002    81 CSVQHASLPEPLLEDW 96

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 1847913971 206 VPPLVKV--THHVTSSV-TTLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTC 282
Cdd:cd05767     1 VPPEVTVfpKSPVELGEpNTLICFVDNFFPPVINVTWLRNGQPV-TDGVSETVFLPREDHSFRKFSYLPFTPSEGDIYDC 79

                          90
                  ....*....|....*.
gi 1847913971 283 QVEHPGLDQPLIVIWE 298
Cdd:cd05767    80 RVEHWGLEEPLLKHWE 95

immunoglobulin domain of neonatal Fc receptor, major histocompatibility complex (MHC)-like; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin domain of neonatal Fc receptor (FcRn). FcRn performs two distinct functions: the transport of maternal immunoglobulin G (IgG) to pre- or neonatal mammals which provides passive immunity and protection of IgG from normal serum protein catabolism. FcRn is related to class I MHC proteins, but lacks a functional peptide binding groove. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1847913971 221 TTLRCRALNYYPQNITMKWLKDKQPMDAKEfepKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEHPGLDQPLIV 295
Cdd:cd21011    20 SVLTCSAFSFYPPELQLRFLRNGLAAGSGE---GDFGPNGDGSFHAWSSLTVKSGDEHHYRCVVQHAGLAQPLTV 91

Immunoglobulin C1-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1847913971 222 TLRCRALNYYPQNITMKWLKDKQPM--DAKEFEPkdvLPNGDGTYQGWITLAVPPGEEQR---YTCQVEHPGL 289
Cdd:pfam07654  16 TLTCLVTGFYPPDITVTWLKNGQEVteGVKTTPP---SPNSDWTYQLSSYLTVTPSDWESgdeYTCRVEHEGL 85

Class II major histocompatibility complex (MHC) beta 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 Class II major histocompatibility complex (MHC) beta chain immunoglobulin domain of histocompatibility antigen (HLA) I-E. 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 molecules have the same basic features insofar as peptide loading and presentation, although each interacts with distinctly different sets of peptides. They also differ in that there is a relatively high incidence of deletion of the I-E gene in both inbred strains of mice as well as wild mice and the lack of the reverse situation i.e. the deletion of I-A genes. A detailed structural understanding of the similarities and differences between I-A and the paralogous I-E could help illuminate the respective roles these molecules play 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. 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 1847913971 204 QQVPPLVKVTHHVTSSV---TTLRCRALNYYPQNITMKWLKDKQPmDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRY 280
Cdd:cd20998     3 RRVEPTVTVYPTKTQPLehhNLLVCSVSDFYPGNIEVRWFRNGKE-EKTGIVSTGLVRNGDWTFQTLVMLETVPQSGEVY 81

                          90
                  ....*....|....*...
gi 1847913971 281 TCQVEHPGLDQPLIVIWE 298
Cdd:cd20998    82 TCQVEHPSLTDPVTVEWK 99

Signal-regulatory protein (SIRP) immunoglobulin-like domain 3; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain in Signal-Regulatory Protein (SIRP), domain 3 (C1 repeat 2). The SIRPs belong to the "paired receptors" class of membrane proteins that comprise several genes coding for proteins with similar extracellular regions but very different transmembrane/cytoplasmic regions with different (activating or inhibitory) signaling potentials. They are commonly on NK cells, but are also on many myeloid cells. Their extracellular region contains three Immunoglobulin superfamily domains a single V-set and two C1-set IgSF domains. Their cytoplasmic tails that contain either ITIMs or transmembrane regions that have positively charged residues that allow an association with adaptor proteins, such as DAP12/KARAP, containing ITAMs. There are 3 distinct SIRP members: alpha, beta, and gamma. SIRP alpha (also known as CD172a or SRC homology 2 domain-containing protein tyrosine phosphatase substrate 1/Shps-1) is a membrane receptor that interacts with a ligand CD47 expressed on many cells and gives an inhibitory signal through immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic region that interact with phosphatases SHP-1 and SHP-2. SIRP beta has a short cytoplasmic region and associates with a transmembrane adapter protein DAP12 containing immunoreceptor tyrosine-based activation motifs to give an activating signal. SIRP gamma contains a very short cytoplasmic region lacking obvious signaling motifs but also binds CD47, but with much less affinity.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 206 VPPLVKVTHHVTS--SVTTLRCRALNYYPQNITMKWLKDKQPMDAKefEPKDVLPNGDGTY--QGWITLAVPPGEEQ-RY 280
Cdd:cd16085     1 VPPTLEVTQQPTMvwNQVNVTCQVEKFYPQRLQLTWLENGNVSRTE--TPSTLTVNKDGTYnwTSWLLVNVSAHREDvVL 78

                          90
                  ....*....|....
gi 1847913971 281 TCQVEHPGldQPLI 294
Cdd:cd16085    79 TCQVEHDG--QPAV 90

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        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 206 VPPLVKVT--HHvtssvTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEpKDVLPNGDGTYQGWITLAVPPGEEQRYTCQ 283
Cdd:cd21003     8 VSPSKKGPlqHH-----NLLVCHVTDFYPGNIQVRWFLNGQEETAGVVS-TNLIHNGDWTFQILVMLEMTPQQGDVYTCQ 81

                          90
                  ....*....|....
gi 1847913971 284 VEHPGLDQPLIVIW 297
Cdd:cd21003    82 VEHPSLDSPVTVEW 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1847913971 221 TTLRCRALNYYPQNITMKWLKDKQPMDAKEF----EPKDvlpNGDGTYQGWITLAVPPGE---EQRYTCQVEHPGL 289
Cdd:cd16093    20 ATFVCLATGFSPKTISFKWLRNGKEVTSSTGavveEPKE---DGKTLYSATSFLTITESEwksQTEFTCEFKHKGE 92

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1847913971 222 TLRCRALNYYPQNITMKWLKDKQPMdAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEHPGLDQPLIVIWE 298
Cdd:cd21008    20 TLICLVDNIFPPVINITWLSNGHSV-TEGVSETSFLSKSDHSFLKISYLTFLPSADDIYDCKVEHWGLDKPLLKHWE 95

CH3 domain (third constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, gamma, and delta chains, and CH4 domain (fourth constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, epsilon, and mu chains; member of the C1-set of I; The members here are composed of the third and fourth immunoglobulin constant domain (IgC) of alpha, delta, gamma and alpha, epsilon, and mu heavy chains, respectively. 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1847913971 222 TLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVLPNGDGTYQGWITLAVPPGEEQR---YTCQVEHPGLDQPLIV 295
Cdd:cd05768    20 TLTCLVKGFYPEDIFVSWLQNGEPLPSADYKTTAPVPESDGSFFVYSKLNVSTADWNSgdvFSCVVGHEALPLQFTQ 96

Class II major histocompatibility complex (MHC) alpha chain immunoglobulin domain of histocompatibility antigen (HLA) I-A; 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-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 molecules have the same basic features insofar as peptide loading and presentation, although each interacts with distinctly different sets of peptides. They also differ in that there is a relatively high incidence of deletion of the I-E a gene in both inbred strains of mice as well as wild mice and the lack of the reverse situation i.e. the deletion of I-A genes. A detailed structural understanding of the similarities and differences between I-A and the paralogous I-E could help illuminate the respective roles these molecules play 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. 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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1847913971 222 TLRCRALNYYPQNITMKWLKDKQPMDAKEFEpKDVLPNGDGTYQGWITLAVPPGEEQRYTCQVEHPGLDQPLIVIW 297
Cdd:cd21006    20 TLICFVDNIFPPVINITWLRNSKSVTDGVYE-TSFLVNRDHSFHKLSYLTFIPSDDDIYDCKVEHWGLEEPVLKHW 94

Immunoglobulin light chain Constant domain; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig) light chain constant (C) domain. 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. There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determine the type of immunoglobulin: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 217 TSSVTTLRCRALNYYPQNITMKWLKDKQPMDAKEFEPKDVlPNGDGTYQGWITLAVPPGE---EQRYTCQVEHPGLDQPL 293
Cdd:cd07699    15 SSGKATLVCLINKFYPGFATVTWKVDGSTVSSGVTTSKTE-QQSDNTYSMSSYLTLSSSDwnkHKVYTCEVTHEGLSSTI 93

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1847913971 223 LRCRALNYYPQNITMKWLKDKQPMDAKEFEPKdVLPNGDGTYQGWITLAVPPGEEQRYTCQVEHPGLDQPLIVIWE 298
Cdd:cd21005    21 LICFIDKFSPPVVNVTWLRNGRPVTEGVSETV-FLPRDDHLFRKFHYLTFLPSTDDFYDCEVDHWGLEEPLRKHWE 95

CH2 domain (second constant Ig domain of the heavy chain) in immunoglobulin E (IgE); member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second constant domain of the heavy chain of immunoglobulin E (IgE). The basic structure of immunoglobulin (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). The different classes of antibodies vary in their heavy chains; the IgE class has the epsilon type. This domain (Cepsilon2) of IgE is in place of the flexible hinge region found in IgG.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1847913971 208 PLVKVTHHVTSSVTT-----LRCRALNYYPQNITMKWLKDKQPMDakefepkDVLPN------GDGTYQGWITLAVPPGE 276
Cdd:cd05847     1 PTVQILHSSCASTLTsetiqLLCLISGYTPSTIEVEWLVDGQVAT-------LSAAStapqkeEGGTFSTTSKLNVTQED 73

                          90
                  ....*....|....*..
gi 1847913971 277 ---EQRYTCQVEHPGLD 290
Cdd:cd05847    74 wksGKTYTCKVTHQGTT 90

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin heavy mu 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 mu 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1847913971 217 TSSVTTLRCRALNYYPQNITMKWLKDKQPM--DAKEFEPkdVLPNgdGTYQGWITLAVPPGE---EQRYTCQVEHPG 288
Cdd:cd21819    14 TSDPVTVGCLATDFLPDSITFSWTDDNNSLttGVKTYPS--VLTG--GTYTASSQLQVPESEwksKENFYCKVEHPG 86