Localization of the binding site for cell attachment in the alpha1(I) chain of collagen

Certain cells such as CHO (Chinese hamster ovary) and fibroblasts attach to a substrate of type I collagen via proteins that link the cell surface to collagen. Serum contains a glycoprotein, c-CAP (collagen cell attachment protein), that can mediate this adhesion. Previously, we established that alpha1(I)-CB7 (cyanogen bromide peptide 7), which lies within residues 552 to 822 of collagen, contains a major binding site for c-CAP(alpha1(I)-CB7 has been renumbered to account for an additional triplet recently identified at residue 613 (P. P. Fietzek and R. W. Glanville, manuscript in preparation). Now we have examined the ability of various peptides derived by proteolytic digestion of alpha1(I)-CB7 to bind to c-CAP based upon their ability to inhibit cell attachment to collagen. The binding site lies within residues 757 to 791. It is likely that this is the sole binding site in the alpha1(I) chain since cleavage of the bond between residues 775 and 776 in the alpha1(I) chain destroys cell attachment activity.