The myosin step size: measurement of the unit displacement per ATP hydrolyzed in an in vitro assay.
The myosin step size: measurement of the unit displacement per ATP hydrolyzed in an in vitro assay.
复制标题
肌球蛋白步长：在体外测定中测量每个 ATP 水解的单位位移。
DOI：
10.1073/pnas.87.18.7130
复制
发表时间：
1990
影响因子：
11.1
通讯作者：
Spudich,JA
中科院分区：
文献类型：
--
作者：
Toyoshima,YY;Kron,SJ;Spudich,JA
肌肉收缩中的化学机械偶联可能是由于“摆动的横桥”，使得肌球蛋白头与肌动蛋白丝结合的角度的变化与ATP水解产物的释放紧密偶联。该模型将限制步长，即由单个ATP水解产生的肌动蛋白的单位位移，小于肌球蛋白头部弦长的两倍。最近的测量发现，步长要显着大于这个几何限制，使任何直接的对应关系的crossbridge和ATP水解循环的问题。我们已经测量了ATP水解率，由于肌动蛋白的滑动运动在体外运动分析由纯化的肌动蛋白和纯化的肌球蛋白。我们已经计算出了一个明显的肌球蛋白步长以及由肌球蛋白头部的大小设置的几何限制。这些数据与肌球蛋白过桥运动和ATP水解之间的紧密耦合是一致的。
Chemomechanical coupling in muscle contraction may be due to "swinging crossbridges," such that a change in the angle at which the myosin head binds to the actin filament is tightly coupled to release of products of ATP hydrolysis. This model would limit the step size, the unit displacement of actin produced by a single ATP hydrolysis, to less than twice the chord length of the myosin head. Recent measurements have found the step size to be significantly larger than this geometric limit, bringing into question any direct correspondence between the crossbridge and ATP-hydrolysis cycles. We have measured the rate of ATP hydrolysis due to actin sliding movement in an in vitro motility assay consisting of purified actin and purified myosin. We have calculated an apparent myosin step size well within the geometric limit set by the size of the myosin head. These data are consistent with tight coupling between myosin crossbridge movement and ATP hydrolysis.