This entry represents the V-set domains, which are Ig-like domains resembling the antibody variable domain. V-set domains are found in diverse protein families, including immunoglobulin light and heavy chains; in several T-cell receptors such as CD2 (Cluster of Differentiation 2), CD4, CD80, and CD86; in myelin membrane adhesion molecules; in junction adhesion molecules (JAM); in tyrosine-protein … expand

This entry represents the V-set domains, which are Ig-like domains resembling the antibody variable domain. V-set domains are found in diverse protein families, including immunoglobulin light and heavy chains; in several T-cell receptors such as CD2 (Cluster of Differentiation 2), CD4, CD80, and CD86; in myelin membrane adhesion molecules; in junction adhesion molecules (JAM); in tyrosine-protein kinase receptors; and in the programmed cell death protein 1 (PD1).

The basic structure of immunoglobulin (Ig) molecules is a tetramer of two light chains and two heavy chains linked by disulphide 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, delta, epsilon, gamma and mu, all consisting of a variable domain (VH) and three (in alpha, delta and gamma) or four (in epsilon and mu) constant domains (CH1 to CH4). Ig molecules are highly modular proteins, in which the variable and constant domains have clear, conserved sequence patterns. The domains in Ig and Ig-like molecules are grouped into four types: V-set (variable; IPR013106 ), C1-set (constant-1; IPR003597 ), C2-set (constant-2; IPR008424 ) and I-set (intermediate; IPR013098 ) [ PUBMED:9417933 ]. Structural studies have shown that these domains share a common core Greek-key β-sandwich structure, with the types differing in the number of strands in the β-sheets as well as in their sequence patterns [ PUBMED:15327963 PUBMED:11377196 ].

Immunoglobulin-like domains that are related in both sequence and structure can be found in several diverse protein families. Ig-like domains are involved in a variety of functions, including cell-cell recognition, cell-surface receptors, muscle structure and the immune system [ PUBMED:10698639 ].