Chiang T M, Kang A H
J Biol Chem. 1976 Oct 25;251(20):6347-51.
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.
已证实人血小板的分离膜可结合源自鸡皮肤胶原蛋白α1(I)链的变性多肽链。该过程是可逆的，且依赖于时间和蛋白质浓度。这种结合具有特异性，缔合常数为1.88×10(-6)M。用胰蛋白酶、糜蛋白酶和链霉蛋白酶预先处理分离膜，会显著抑制14C标记的α1链结合，但神经氨酸酶或胶原酶处理则无影响。结合放射性的解离以及随后在羧甲基纤维素和琼脂糖A - 1.5m上的色谱分析表明，α1链未发生改变。Scatchard图分析表明，每个血小板大约有20,000个结合位点。α1链的结合受到源自α1、α1 - CB5的糖肽以及纯化的葡糖基半乳糖基羟赖氨酸的抑制，但不受α1的其他溴化氰肽（即α1 - CB3、- CB4、- CB7和- CB8）的影响。动力学研究表明，羟赖氨酸糖苷的抑制作用具有竞争性。α1诱导的血小板聚集剂量反应曲线与血小板膜对α1的结合密切相关。这些结果表明，血小板膜上存在胶原α1链的特异性结合位点，且α1链的碳水化合物部分在结合中起作用。这些发现还支持了鸡皮肤α1链通过作用于血小板膜介导血小板聚集和释放反应的假说。
