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. This 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 binding site on ON for type V collagen is distal from the site of N-glycosylation in terms of amino acid sequence but may be proximal in the folded, fully glycosylated, three-dimensional structure. Consistent with this conclusion is the ability of a synthetic peptide consisting of amino acids 1-17 to specifically inhibit the binding of ON to type V collagen.