Unraveling the amino acid sequence crucial for heparin binding to collagen V

Abstract

We have previously shown that a recombinant 12-kDa fragment of the collagen α1(V) chain (Ile824-Pro950), referred to as HepV, binds to heparin and heparan sulfate (Delacoux, F., Fichard, A., Geourjon, C., Garrone, R., and Ruggiero, F. (1998) J. Biol. Chem. 273, 15069-15076). No consensus sequence was found in the α1(V) primary sequence, but a cluster of 7 basic amino acids (in the Arg900-Arg924 region) was postulated to contain the heparin-binding site. The contribution of individual basic amino acids within this sequence was examined by site-directed mutagenesis. Further evidence for the precise localization of the heparin-binding site was provided by experiments based on the fact that heparin can protect the α1(V) chain heparin-binding site from trypsin digestion. The results parallel the alanine scanning mutagenesis data, i.e. heparin binding to the α1(V) chain involved Arg912, Arg918, and Arg921 and two additional neighboring basic residues, Lys905 and Arg909. Our data suggest that this extended sequence functions as a heparin-binding site in both collagens V and XI, indicating that these collagens use a novel sequence motif to interact with heparin.