Isolation and purification of collagen alpha 1(I) receptor from human platelet membrane.

We have previously demonstrated that chick-skin type I collagen and the alpha 1(I) chain mediate platelet aggregation. Aggregation was associated with specific binding of these substances by platelet membranes. We now describe the isolation and purification of the receptor from isolated human platelet membrane. The receptor can be solubilized from platelet membranes with 0.5% Triton or 0.5% sodium deoxycholate. Using the combination of gel filtration, affinity column chromatography on alpha 1-Sepharose 4B, and preparative slab gel electrophoreses, the receptor protein can be purified to a single band as judged on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its activity sulfate-polyacrylamide gel electrophoresis. Its activity was destroyed by incubation with trypsin or Pronase. The apparent molecular weight was estimated to be 65,000 by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Bound [14C]glycine-labeled alpha 1(I) is displaced by unlabeled alpha 1 chain. The binding of [14C]glycine-labeled alpha 1(I) by the purified alpha 1(I) receptor can also be inhibited by the receptor isolated from type I fibrillar collage-Sepharose affinity chromatography. The data suggest that the alpha 1(I) binding site is identical with the type I fibrillar collagen binding site.