Platelet adhesion to type I collagen and alpha 1 (I)3 trimers: involvement of the C-terminal alpha 1 (I) CB6A peptide

The adhesion of human platelets to calf-skin acid-soluble and pepsin extracted type I and type III collagens has been determined. In fibrillar form, all three preparations were equiactive. Modification of their charge pattern (methylation, deamidation) diminished or abolished platelet adhesiveness. Alpha 1(I) and alpha 2 chains, isolated from type I collagen by preparative PAGE followed by CMC chromatography, did not induce the adhesion of platelets. After reassociation as fibrillar trimers, (alpha 1(I))3 fibrils were active while (alpha 2)3 were not, suggesting that in the ordered structure required for platelet adhesion to type I collagen, the alpha 1 chains are essential. Platelets adhered significantly to alpha 1(I) CB6 peptide obtained by the cyanogen bromide cleavage of alpha 1(I) chains : the adhesive properties of type I collagen therefore seems to be associated with the C terminal end of the alpha 1 chains.