Characterization of the active site of platelet myosin in comparison to smooth and skeletal muscle myosin.
Characterization of the active site of platelet myosin in comparison to smooth and skeletal muscle myosin.
复制标题
与平滑肌和骨骼肌肌球蛋白相比，血小板肌球蛋白活性位点的表征。
DOI：
10.1016/0003-9861(76)90505-1
复制
发表时间：
1976
影响因子：
3.9
通讯作者：
A. Mühlrád
中科院分区：
文献类型：
--
作者：
I. Cohen;E. Kaminski;R. Lamed;A. Oplatka;A. Mühlrád
在Ca2+和Mg2+不存在和存在的情况下，来自人血小板和鸡胗的重肌球蛋白亚片段-1在琼脂糖- atp柱上表现出相同的色谱模式。Ca2+存在时，其行为与兔白色骨骼肌亚片段-1不同。血小板肌球蛋白赖氨酸残基与2,4,6-三硝基苯磺酸盐的反应不影响K+或Mg2+刺激的atp酶活性。鸡胗肌球蛋白也表现出类似的行为，而骨骼肌肌球蛋白中更活跃的赖氨酸残基的三硝基苯基化导致Mg2+刺激的atp酶活性显著增加，K+刺激的atp酶活性显著降低。这些特征可能表明必需赖氨酸残基在血小板和平滑肌肌球蛋白中的位置相似，而不同于骨骼肌。在没有添加核苷酸的情况下，用n -乙基马来酰亚胺烷基化巯基导致所有三种肌球蛋白中K+- atp酶的损失和Ca2+- atp酶的增加，骨骼肌球蛋白的增加远远大于血小板和鸡胗制剂。在MgADP的存在下，肌球蛋白的烷基化导致所有制剂的K+- atp酶降低，而血小板和骨骼肌蛋白的Ca2+- atp酶随时间的变化最大。这些特征可能表明血小板和平滑肌肌球蛋白的活性部位有一定的相似性，而它们与骨骼肌肌球蛋白之间存在差异。
Heavy meromyosin subfragment-1 from human platelets and chicken gizzard exhibited an identical chromatographic pattern on agarose-ATP columns both in the absence and in the presence of Ca2+and Mg2+. In the presence of Ca2+, the behavior differed from that of rabbit white skeletal muscle subfragment-1. The reaction of lysyl residues of platelet myosin with 2,4,6-trinitrobenzene sulfonate did not affect the K+- or Mg2+-stimulated ATPase activity. A similar behavior was exhibited by chicken gizzard myosin whereas trinitrophenylation of the more active lysyl residues in skeletal muscle myosin caused a marked increase in Mg2+-stimulated and a decrease in K+-stimulated ATPase activity. These features may point to a similar location of the essential lysyl residue in platelet and smooth muscle myosin, which is different from that of skeletal muscle. Alkylation of thiol groups byN-ethyl maleimide in the absence of added nucleotides resulted in a loss of K+-ATPase and in an increase in the Ca2+-ATPase in all three myosins, the increase for the skeletal myosin being much greater than for the platelet and chicken gizzard preparations. Alkylation of myosin in the presence of MgADP led to a decrease in K+-ATPase of all preparations whereas the Ca2+-ATPase as a function of time exhibited a maximum for the platelet and skeletal muscle proteins. These features may point to a certain similarity with respect to the active site of platelet and smooth muscle myosins and a difference between these and skeletal muscle myosin.