Met, an HGF Receptor/Met type protein kinase, is a cell-surface proto-oncogene that mediates the biological activities of hepatocyte growth factor. The protein is a disulfide-linked heterodimer comprised of two subunits: a 50kD extracellular alpha subunit and a membrane-spanning 145kD beta subunit that binds ligand. Met is an important regulator of cell proliferation and differentiation, organ regeneration, embryogenesis, and tumorogenesis. Constitutive activation mutations of the met gene lead to many cancers, particularly renal papillary carcinoma.