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.

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gi 2322547347  21 EPSVYELEStNKSHPLSACLFTDyFPGNINVSAT-GSNLVGIESSVVV---VEDQASYGAVLWQNA 82
Cdd:cd07688     1 EPAVYQLKD-PRSSDISVCLFTD-FDSQTNVTKSmDSETVFITNKTVLdmkSMDSKSNGAVAWSNQ 64

Immunoglobulin (Ig) constant domain the alpha chain of alpha/beta T-cell antigen receptors (TCRs); The members here are composed of the constant domain of the alpha chain of alpha/beta T-cell antigen receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes and are composed of alpha and beta, or gamma and delta polypeptide chains with variable (V) and constant (C) regions. This group includes the variable domain of the alpha chain. Alpha/beta TCRs recognize antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. The antigen binding site is formed by the variable domains of the alpha and beta chains, located at the N-terminus of each chain. Alpha/beta TCRs recognize antigens differently from gamma/delta TCRs.

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gi 2322547347  21 EPSVYELEStNKSHPLSACLFTDyFPGNINVSAT-GSNLVGIESSVVV---VEDQASYGAVLWQNA 82
Cdd:cd07688     1 EPAVYQLKD-PRSSDISVCLFTD-FDSQTNVTKSmDSETVFITNKTVLdmkSMDSKSNGAVAWSNQ 64

Immunoglobulin (Ig) constant domain the alpha chain of alpha/beta T-cell antigen receptors (TCRs); The members here are composed of the constant domain of the alpha chain of alpha/beta T-cell antigen receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes and are composed of alpha and beta, or gamma and delta polypeptide chains with variable (V) and constant (C) regions. This group includes the variable domain of the alpha chain. Alpha/beta TCRs recognize antigen as peptide fragments presented by major histocompatibility complex (MHC) molecules. The antigen binding site is formed by the variable domains of the alpha and beta chains, located at the N-terminus of each chain. Alpha/beta TCRs recognize antigens differently from gamma/delta TCRs.

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gi 2322547347  21 EPSVYELEStNKSHPLSACLFTDyFPGNINVSAT-GSNLVGIESSVVV---VEDQASYGAVLWQNA 82
Cdd:cd07688     1 EPAVYQLKD-PRSSDISVCLFTD-FDSQTNVTKSmDSETVFITNKTVLdmkSMDSKSNGAVAWSNQ 64

CH1 domain (first constant Ig domain of the heavy chain) in immunoglobulin heavy alpha, delta, epsilon, gamma, and mu chains; member of the C1-set of Ig superfamily (IgSF) domains; The members here are 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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gi 2322547347  22 PSVYELESTNKSHPLS----ACLFTDYFPGNINVSATGSNLVGIESSVV 66
Cdd:cd04985     2 PTVFPLQSATKSQSNGpvalGCLISDYFPESITVSWQKNTNSITSGFTR 50