Immunoglobulin (Ig)-like domain in the polymeric Ig receptor (pIgR) and similar domains
Ig_pIgR: Immunoglobulin (Ig)-like domain in the polymeric Ig receptor (pIgR) and similar domains. pIgR delivers dimeric IgA and pentameric IgM to mucosal secretions. Polymeric immunoglobulin (pIgs) are the first defense against pathogens and toxins. IgA and IgM can form polymers via an 18-residue extension at their c-termini referred to as the tailpiece. pIgR transports pIgs across mucosal epithelia into mucosal secretions. Human pIgR is a glycosylated type I transmembrane protein, comprised of a 620 residue extracellular region, a 23 residue transmembrane region, and a 103 residue cytoplasmic tail. The extracellular region contains five domains that share sequence similarity with Ig variable (v) regions. This group also contains the Ig-like extracellular domains of other receptors such as NK Cell Receptor Nkp44 and myeloid receptors, among others.