The sequence signature of an Ig-fold

Ig superfamily (IgSF) constitutes the largest superfamily in human genome. In particular, Ig-like domains are the most abundant structural module within cell surface receptors, functioning in nervous as well as immune system. Here I describe some key sequence signature of an I-set Ig-like domain from known structures of IgSF members. These signature residues define the I-set Ig-like domain, which should aid structural and functional studies of cell surface receptors.