Immunochemical analysis of Acanthamoeba myosins IA, IB, and II.
Immunochemical analysis of Acanthamoeba myosins IA, IB, and II.
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棘阿米巴肌球蛋白 IA、IB 和 II 的免疫化学分析。
DOI：
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发表时间：
1979
影响因子：
4.8
通讯作者：
E. Korn
中科院分区：
文献类型：
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作者：
H. Gadasi;E. Korn
卡氏棘阿米巴提取物含有三种肌球蛋白同工酶，它们的天然分子量、亚基组成和酶性质不同。其重链的肽图谱此前提供了强有力的证据，证明这三种肌球蛋白是不同基因的产物。这些结论现已通过免疫化学研究得到扩展。在放射免疫沉淀测定中，针对肌球蛋白 II 产生的抗体与其发生反应，但不与肌球蛋白 IA 或肌球蛋白 IB 发生反应，并且针对肌球蛋白 IA 或肌球蛋白 IB 产生的抗体不与肌球蛋白 II 发生反应。针对肌球蛋白 IA 或 IB 的抗体与肌球蛋白 IA 和 IB 均发生反应，但这两种同工酶仍然可以通过竞争性放射免疫测定和其他标准在免疫化学上区分。同样，肌球蛋白 II 抗体抑制肌球蛋白 II 的肌动蛋白激活的 Mg+ATP 酶活性，但不抑制肌球蛋白 IA 的活性，而肌球蛋白 IA 和 IB 的抗体抑制肌球蛋白 IA 的肌动蛋白激活的 Mg'+ ATP 酶活性，但不抑制肌球蛋白 II 的肌动蛋白激活的 Mg'+ ATP 酶活性。细胞提取物与抗体的直接免疫沉淀以及整个变形虫的十二烷基硫酸钠-聚丙烯酰胺电泳凝胶与抗体和“β-蛋白A”的反应证实了这些观察结果，并且还表明至少是肌球蛋白IA和IB的重链具有共同的抗原位点。此外，后面这些实验提供的数据与早期的证据相一致，尽管 由于其重链的分子量异常低，分离的肌球蛋白很可能是细胞中存在的天然分子。
Extracts of Acanthamoeba castellanii contain three myosin isoenzymes which differ in native molecular weight, subunit composition, and enzymatic properties. Peptide mapping of their heavy chains had previously provided strong evidence that the three myosins are products of different genes. These conclusions have now been extended by immunochemical studies. In the radioimmunoprecipitation assay, antibodies raised against myosin II react with it, but not with myosin IA or myosin IB, and antibodies raised against either myosin IA or myosin IB do not react with myosin II. Antibodies raised against either myosin IA or IB react with both myosins IA and IB, but these two isoenzymes are, nonetheless, immunochemically distinguishable by competitive radioimmunoassay and other criteria. Similarly, myosin II antibodies inhibit the actin-activated Mg+ATPase activity of myosin II, but not that of myosin IA, while antibodies to myosins IA and IB inhibit the actin-activated Mg’+ATPase activity of myosin IA, but not that of myosin II. Direct immunoprecipitation of cell extracts with antibodies and reaction of sodium dodecyl sulfate-polyacrylamide electrophoretic gels of whole amoebae with antibodies and “?-protein A confirm these observations and also show that it is at least the heavy chains of myosins IA and IB that have common antigenic sites. Furthermore, these latter experiments provide data compatible with earlier evidence that, despite the unusually low molecular weights of their heavy chains, the isolated myosins are likely to be the native molecules as they exist in the cell.