title: Binding of chick skin collagen alpha 1 chain by isolated membranes from human platelets.
abstract: Binding of a denaturated polypeptide chain derived from chick skin collagen, the alpha 1(I) chain, by isolated membranes of human platelets has been demonstrated. The process is reversible, and time- and protein concentration-dependent. The binding is specific, with an association constant of 1.88 X 10(-6) M. Prior treatment of the isolated membranes with trypsin, chymotrypsin, and pronase, resulted in significant inhibition of the 14C-labeled alpha 1 chain binding, but neuraminidase or collagenase treatment had no effect. Dissociation of the bound radioactivity and subsequent chromatographic analyses on carboxymethylcellulose and agarose A-1.5m revealed that the alpha 1 chain was unaltered. Scatchard plot analysis suggested that there are approximately 20,000 binding sites per platelet. The binding of the alpha 1 chain was inhibited by a glycopeptide derived from alpha 1, alpha 1-CB5 and by purified glucosylgalactosyl hydroxylysine, but was not affected by other cyanogen bromide peptides of alpha 1, namely alpha 1-CB3, -CB4, -CB7, and -CB8. Kinetic studies demonstrated that inhibition by the hydroxylysine glycoside is competitive. Dose-response curves of platelet aggregation induced by alpha 1 and the binding of alpha 1 by platelet membranes correlate closely. These results indicate that there are specific binding sites for collagen alpha 1 chain on platelet membranes, and that the carbohydrate moiety of the alpha 1 chain plays a role in the binding. The findings also support the hypothesis that the chick skin alpha 1 chain mediates platelet aggregation and the release reaction by acting on platelet membranes.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D003094:Collagen / Q000097:blood*; D003488:Cyanogen Bromide; D006801:Humans; D007700:Kinetics; D007842:Lathyrism / Q000378:metabolism; D010446:Peptide Fragments / Q000097:blood; D010974:Platelet Aggregation; D011485:Protein Binding; D012867:Skin / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D003094:Collagen; D003488:Cyanogen Bromide