Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. 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 by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  20 VLTQPPSASGTPGQRVTISCSGSSSNIGSNTVNWYQQLPGTAPKLLIYSNNKRPSGVPDRFSGSKSGTSASLAISGLQSE 99
Cdd:cd04984     1 VLTQPSSLSVSPGETVTITCTGSSGNISGNYVNWYQQKPGSAPRYLIYEDKHRPSGIPDRFSGSKSGNTASLTISGAQTE 80

                          90
                  ....*....|...
gi 2558071154 100 DEADYYCAAWDDS 112
Cdd:cd04984    81 DEADYYCQVWDSN 93

Immunoglobulin (Ig) lambda light chain variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, lambda type, variable (V) domain. 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 composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: 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. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  20 VLTQPPSASGTPGQRVTISCSGSSSNIGSNTVNWYQQLPGTAPKLLIYSNNKRPSGVPDRFSGSKSGTSASLAISGLQSE 99
Cdd:cd04984     1 VLTQPSSLSVSPGETVTITCTGSSGNISGNYVNWYQQKPGSAPRYLIYEDKHRPSGIPDRFSGSKSGNTASLTISGAQTE 80

                          90
                  ....*....|...
gi 2558071154 100 DEADYYCAAWDDS 112
Cdd:cd04984    81 DEADYYCQVWDSN 93

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  22 TQPPSASGTPGQRVTIS-CSGSSSNIGSNTVNWYQQLPGTAPKLLI--YSNNKRPSGVPDRFSGSK--SGTSASLAISGL 96
Cdd:pfam07686   1 QTPREVTVALGGSVTLPcTYSSSMSEASTSVYWYRQPPGKGPTFLIayYSNGSEEGVKKGRFSGRGdpSNGDGSLTIQNL 80

                          90
                  ....*....|....*.
gi 2558071154  97 QSEDEADYYCAAWDDS 112
Cdd:pfam07686  81 TLSDSGTYTCAVIPSG 96

Immunoglobulin (Ig) lambda light chain variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, lambda type, variable (V) domain. 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 composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: 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. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  20 VLTQPPSASGTPGQRVTISCSGSSSNIGSNTVNWYQQLPGTAPKLLIYSNNKRPSGVPDRFSGSKSGTSASLAISGLQSE 99
Cdd:cd04984     1 VLTQPSSLSVSPGETVTITCTGSSGNISGNYVNWYQQKPGSAPRYLIYEDKHRPSGIPDRFSGSKSGNTASLTISGAQTE 80

                          90
                  ....*....|...
gi 2558071154 100 DEADYYCAAWDDS 112
Cdd:cd04984    81 DEADYYCQVWDSN 93

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E and, D strands in one sheet and A', G, F, C, C', and C" strands in the other.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  21 LTQPP-SASGTPGQRVTISCSGSSSNIGSNtVNWYQQLPGTAPKLLIYSN---NKRPSGVPDRFSGSKSG-TSASLAISG 95
Cdd:cd00099     1 VTQSPrSLSVQEGESVTLSCEVSSSFSSTY-IYWYRQKPGQGPEFLIYLSsskGKTKGGVPGRFSGSRDGtSSFSLTISN 79

                          90       100
                  ....*....|....*....|.
gi 2558071154  96 LQSEDEADYYCAAWDDSLNGP 116
Cdd:cd00099    80 LQPEDSGTYYCAVSESGGTDK 100

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) gamma chain; The members here are composed of the immunoglobulin (Ig) variable (V) domain of the gamma chain of gamma/delta T-cell receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are heterodimers consisting of alpha and beta chains or gamma and delta chains. Each chain contains a variable (V) and a constant (C) region. The majority of T cells contain alpha/beta TCRs, but a small subset contain gamma/delta TCRs. Alpha/beta TCRs recognize antigens as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Gamma/delta T cells can also be stimulated by non-peptide antigens such as small phosphate- or amine-containing compounds. The variable domain of gamma/delta TCRs is responsible for antigen recognition and is located at the N-terminus of the receptor. Members of this group contain the standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  21 LTQPP-SASGTPGQRVTISCSGSSSNIGSNTVNWYQQLPGTAPKLLIY----SNNKRPSG-VPDRFSGSK-SGTSAS-LA 92
Cdd:cd04982     1 LEQPQlSITREESKSVTISCKVSGIDFSTTYIHWYRQKPGQALERLLYvsstSAVRKDSGkTKNKFEARKdVGKSTStLT 80

                          90
                  ....*....|....*...
gi 2558071154  93 ISGLQSEDEADYYCAAWD 110
Cdd:cd04982    81 ITNLEKEDSATYYCAYWE 98

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154  22 TQPPSASGTPGQRVTIS-CSGSSSNIGSNTVNWYQQLPGTAPKLLI--YSNNKRPSGVPDRFSGSK--SGTSASLAISGL 96
Cdd:pfam07686   1 QTPREVTVALGGSVTLPcTYSSSMSEASTSVYWYRQPPGKGPTFLIayYSNGSEEGVKKGRFSGRGdpSNGDGSLTIQNL 80

                          90
                  ....*....|....*.
gi 2558071154  97 QSEDEADYYCAAWDDS 112
Cdd:pfam07686  81 TLSDSGTYTCAVIPSG 96

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2558071154   24 PPSASGTPGQRVT---ISCSGSSSnigsnTVNWYQQlpgtAPKLLIYsnnkrpsgvPDRFSGSKSGTSASLAISGLQSED 100
Cdd:smart00410   1 PPSVTVKEGESVTlscEASGSPPP-----EVTWYKQ----GGKLLAE---------SGRFSVSRSGSTSTLTISNVTPED 62

                           90
                   ....*....|..
gi 2558071154  101 EADYYCAAWDDS 112
Cdd:smart00410  63 SGTYTCAATNSS 74

Immunoglobulin (Ig)-like variable (V) domain of Cluster of Differentiation (CD) 8 alpha chain; The members here are composed of the immunoglobulin (Ig)-like variable domain of the Cluster of Differentiation (CD) 8 alpha. The CD8 glycoprotein plays an essential role in the control of T-cell selection, maturation, and the T-cell receptor (TCR)-mediated response to peptide antigen. CD8 is comprised of alpha and beta subunits and is expressed as either an alpha/alpha or alpha/beta dimer. Both dimeric isoforms can serve as a coreceptor for T cell activation and differentiation, however they have distinct physiological roles, different cellular distributions, unique binding partners, etc. Each CD8 subunit is comprised of an extracellular domain containing a V-type Ig-like domain, a single pass transmembrane portion, and a short intracellular domain. The Ig domain of CD8 alpha binds to antibodies. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 2558071154  51 VNWYQQLPGTAPK---LLIYSNNKRPSGVPD----RFSGSKSGTSASLAISGLQSEDEADYYCAA 108
Cdd:cd05720    30 CSWLFQPRGSAPQptfLLYLSSSNKTKWAEGldskRFSGSRSGSSYVLTLKDFRKEDEGYYFCSV 94

T-cell receptor Mu, Heavy chain, variable (V) domain; The members here are composed of the immunoglobulin (Ig) heavy chain (H), variable (V) domain of the T-cell receptor Mu. 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 determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which can associate with any of the heavy chains. This family includes alpha, gamma, delta, epsilon, and mu heavy chains. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 2558071154  51 VNWYQQLPGTAPKLLIYSNNKRPSGVPDRFSGSKSGTSA--SLAISGLQSEDEADYYCA 107
Cdd:cd16095    34 LSWYLWVPGHAPLWLTSLDHISTKVSEDRITSSREDTNSqiFLQIKGLGLRDSGQYHCA 92