Deletion of kringle domains or the N-terminal hairpin structure in hepatocyte growth factor results in marked decreases in related biological activities.

To determine the essential domain for biological activity in the hepatocyte growth factor (HGF) molecule, we prepared various mutated recombinant HGFs using site-directed mutagenesis, and examined the effects on DNA synthesis in hepatocytes, scattering of MDCK cells and the antiproliferative activity on HepG2 hepatoma cells. Native HGF and mutant HGFs, in which Gln534 and/or Tyr673 were respectively substituted for His and Ser to coincide with the catalytic triad amino acids in plasmin, markedly stimulated DNA synthesis of hepatocytes and scattering of MDCK cells but inhibited DNA synthesis of HepG2 cells. The mutant HGF deleted with the third or fourth kringle domain resulted in marked decrease of all three biological activities, while deletion of the N-terminal hairpin structure or the first or second kringle domain almost completely inactivated biological activities. We propose that the N-terminal hairpin structure and the first and second kringle domains are essential for biological activities of HGF and possibly for binding to its receptor.