IDENTIFICATION OF HEPARIN-BINDING STRETCHES OF A NATURALLY-OCCURRING DELETED VARIANT OF HEPATOCYTE GROWTH-FACTOR (DHGF)

A deleted variant of hepatocyte growth factor (dHGF) is a naturally oc curring major variant of HGF, which lacks five consecutive amino acid residues in the first kringle domain. While both HGF and dHGF bind to heparin, the residues involved in the binding to heparin have not been identified in either protein. To identify the residues involved in th e binding, we made a series of dHGF mutants in which basic residues in the N-terminal and the first kringle domains were replaced with alani ne residue. The analysis of heparin-binding ability revealed that thre e stretches, (RCTRNK)-R-42 in the hairpin loop structure, and (RKRR)-R -2 and (KIKTKK)-K-27 in the N-terminal basic region, are involved in t he binding. Alanine substitution of each basic residue except K-3 and K-27 in the stretches reduced the heparin-binding ability of dHGF, and the decrease was additive. Conversely, lysine substitution of D-37, ( 38)Q or (64)Q in the N-terminal domain increased heparin-binding abili ty. These results suggest that stretches distant from each other in th e primary structure come into close proximity when the polypeptide fol ds into protein, and form a heparin-binding site with clusters of basi c residues. (C) 1998 Elsevier Science B.V.