Identification and separation of secreted platelet proteins by isoelectric focusing. Evidence that low-affinity platelet factor 4 is converted to beta-thromboglobulin by limited proteolysis.
Identification and separation of secreted platelet proteins by isoelectric focusing. Evidence that low-affinity platelet factor 4 is converted to beta-thromboglobulin by limited proteolysis.
复制标题
通过等电聚焦鉴定和分离分泌的血小板蛋白。
作者：
S. Niewiarowski;D. Walz;P. James;B. Rucinski;F. Kueppers
低亲和力血小板因子4和β -血小板球蛋白是具有共同抗原决定因子的低分子量血小板分泌蛋白。4个氨基酸（Asn-Leu-Ala-Lys）在β -血栓球蛋白的氨基端被删除，但剩下的两个肽的序列似乎是相同的。低亲和力血小板因子4和β -血栓球蛋白在pH 8.0和pH 7.0时具有各自的等电点。两种蛋白的鉴定、定量和分离是通过制备等电聚焦和抗低亲和血小板因子4抗体特异性放射免疫测定相结合的方法实现的。已经确定，由离子载体A23187或凝血酶诱导的血小板聚集后的上清过程含有约80%的低亲和力血小板因子4,8%的β -血小板球蛋白和12%的高阳离子免疫反应物质（血小板碱性蛋白）。实验证据表明，低亲和力血小板因子4最初由血小板分泌，然后由血小板衍生的热不稳定蛋白酶转化为β -血小板球蛋白，该蛋白酶被苯基甲基磺酰氟抑制。
Low-affinity platelet factor 4 and beta-thromboglobulin are low molecular weight platelet secretory proteins that have common antigenic determinants. Four amino acids (Asn-Leu-Ala-Lys) at the amino terminus of beta-thromboglobulin are deleted, but the remaining sequences of the two peptides appear to be identical. Low-affinity platelet factor 4 and beta-thromboglobulin have respective isoelectric points at pH 8.0 and at pH 7.0. Identification, quantitation, and separation of both proteins was achieved by a method combining preparative isoelectric focusing and specific radioimmunoassay with anti-low-affinity platelet factor 4 antibody. It has been determined that the supernate processes immediately after platelet aggregation induced by ionophore A23187 or thrombin contains approximately 80% low-affinity platelet factor 4, 8% beta-thromboglobulin, and 12% highly cationic immunoreactive material (platelet basic protein). Experimental evidence suggests that low-affinity platelet factor 4 is originally secreted by platelets and then converted to beta-thromboglobulin by a platelet-derived, heat-labile protease that is inhibited by phenylmethylsulfonyl fluoride.