The immunoglobulin superfamily (IgSF) is a large group of proteins that have a similar tertiary structure
, the immunoglobulin fold, which is a beta-sandwich
that can have a varying number of strands. These largely carry out functions in the immune system
, in cell
-cell recognition or in structural organization of muscle
. First detected by sequence homology
, it has since been verified experimentally that they all have this sandwich structure. IgSF proteins are all about 100 amino acids long
and contain a conserved disulfide
packed against a tryptophan
. This central structure motif is also known as 'the pin'.
All antibodies are made up of several Ig domains (such as Immunoglobulin E (IgE). They are also a central component in many extracellular domains of cell surface receptors.