PDZ domains (also known as Discs-large homologous regions (DHR) or GLGF)) are found in diverse signalling proteins in bacteria, yeasts, plants, insects and vertebrates. PDZ domains can occur in one or multiple copies and are nearly always found in cytoplasmic proteins. They bind either the carboxyl-terminal sequences of proteins or internal peptide sequences. In most cases, interaction between a PDZ domain and its target is constitutive, with a binding affinity of 1 to 10 microns. PDZ domains consist of 80 to 90 amino acids comprising six beta-strands (beta-A to beta-F) and two alpha-helices, A and B, compactly arranged in a globular structure. Peptide binding of the ligand takes place in an elongated surface groove as an anti-parallel beta-strand interacts with the beta-B strand and the B helix. The structure of PDZ domains allows binding to a free carboxylate group at the end of a peptide through a carboxylate-binding loop between the beta-A and beta-B strands.
Proteins containing this domain