Evolution of plasminogen-related growth factors (HGF/SF and HGF1/MSP)

HGF/SF and HGF1/MSP define a novel growth factor family whose members share the domain structure and the proteolytic process of activation of the blood proteinase precursor plasminogen. The amino acid and RNA sequences of HGF/SF and HGF1/MSP, the intron-exon organization of their genes and the predicted 3D structure of individual domains indicate that HGF/SF and HGF1/MSP evolved along with plasminogen and other members of the kringle-serine proteinase (KSP) superfamily from an ancestral gene that contained a single copy of the kringle domain, a serine proteinase domain and an activation peptide connecting the two domains. A series of intragenic duplications of the kringle domain, gene duplications, exon shuffling and deletions is responsible for the genes currently present in mammals, avians and amphibians. Plasminogen, HGF/SF and HGF1/MSP represent paradigmatic examples of the modern, multi-domain proteins typically associated with vertebrate organisms and illustrate a novel evolutionary pathway that led to the emergence of molecules with growth regulatory activity from proteolytic enzymes.