Cross-bridge movement and the conformational state of the myosin hinge in skeletal muscle.
Cross-bridge movement and the conformational state of the myosin hinge in skeletal muscle.
复制标题
骨骼肌中的跨桥运动和肌球蛋白铰链的构象状态。
DOI：
10.1016/0022-2836(81)90350-8
复制
发表时间：
1981
影响因子：
5.6
通讯作者：
Harrington,WF
中科院分区：
文献类型：
--
作者：
Ueno,H;Harrington,WF
我们修改并扩展了我们早期在肌肉粗丝中交联肌球蛋白片段的程序，以便：(1) 遵循作为 pH 函数的 subfragment-2 和轻肌球蛋白区域交联的时间过程； (2) 消除十二烷基硫酸钠/聚丙烯酰胺凝胶分析中分子内交联的影响。从兔甘油化僵硬肌原纤维中肌球蛋白 S-2† 和 LMM 区域的交联动力学中，我们发现交联的归一化速率 (k S− 2 k LMM) 落在较窄的 pH 范围内（7.4 至 8.4），其 S 形曲线与之前观察到的 subfragment-1 亚基交联的 pH 依赖性非常相似。这一结果与我们之前的结论相反（Sutoh 等人，1978a；Chiao 和 Harrington，1979），即在这些条件下 S-2 连接的主要部分固定在表面上，并表明当 pH 值升高时，该片段与 S-1 亚基一样被释放并远离粗丝表面。 S-2 的这种释放是高度协作的，并且似乎伴随着轻部分肌球蛋白-重部分肌球蛋白铰链内的多肽链构象转变为更开放的结构，如对胰凝乳蛋白酶解的敏感性增加所示。将协同释放过程处理为两种状态平衡表明，当横桥从粗丝表面分离时，发生相当于仅释放约两个质子的电荷变化。
We have modified and extended our earlier procedure for cross-linking myosin segments in the thick filaments of muscle so as to:(1) follow the time-course of cross-linking the subfragment-2 and light meromyosin regions as a function of pH; and (2) eliminate the contribution of intramolecular cross-linking in the analysis of the sodium dodecyl sulfate/polyacrylamide gels. From the kinetics of cross-linking the S-2† and LMM regions of myosin in glycerinated rigor myofibrils of rabbit we find that the normalized rate (k S− 2 k LMM) of cross-linking falls over a narrow range of pH (7.4 to 8.4) with a sigmoidal profile closely similar to that observed earlier for the pH dependence of cross-linking of the subfragment-1 subunits. This result is contrary to our earlier conclusion (Sutoh et al., 1978a; Chiao & Harrington, 1979) that a major fraction of the S-2 link is immobilized on the surface under these conditions, and suggests that this segment, like the S-1 subunit, is released and swings away from the thick filament surface when the pH is raised. This release of S-2 is highly co-operative and appears to be accompanied by a conformational transition of the polypeptide chains within the light meromyosin-heavy meromyosin hinge to a more open structure, as shown by an increased susceptibility to chymotryptic proteolysis. Treatment of the co-operative release process as a two-state equilibrium reveals that a change in charge equivalent to release of only about two protons occurs when the cross-bridge is detached from the surface of the thick filament.