ELEMENTS WITHIN THE FIRST 17 AMINO-ACIDS OF HUMAN OSTEONECTIN ARE RESPONSIBLE FOR BINDING TO TYPE-V COLLAGEN

The region in human osteonectin (ON) responsible for binding to type V collagen has been identified as the first 17 NH2-terminal residues. T his conclusion is based upon binding studies with deletion mutants of ON produced in Escherichia coli, in which parts of the first 17 amino acids have been removed. Wild-type ON from E. coli and mammalian cell- derived nonglycosylated ON bind identically to type V collagen and at least twice as effectively as mammalian cell-derived N-glycosylated ON . In previous studies, it was shown that N-glycosylation at residue 99 significantly reduces the capacity of ON to bind to type V collagen. Results reported in this communication demonstrate that the actual bin ding site on ON for type V collagen is distal from the site of N-glyco sylation in terms of amino acid sequence but may be proximal in the fo lded, fully glycosylated, three-dimensional structure. Consistent with this conclusion is the ability of a synthetic peptide consisting of a mino acids 1-17 to specifically inhibit the binding of ON to type V co llagen.