 A 170 amino acid domain, the so-called MAM (meprin, A-5 protein, and receptor protein-tyrosine phosphatase mu) domain, has been recognised in the extracellular region of functionally diverse proteins.These proteins have a modular, receptor-like architecture comprising a signal peptide, an N-terminal extracellular domain, a single transmembrane domain and an intracellular domain.Such proteins include meprin (a cell surface glycoprotein); A5 antigen (a developmentally-regulated cell surface protein; "Xenopus" nrp1; ); and receptor-like tyrosine protein phosphatase.