平滑肌肌球蛋白横桥相互作用在体外调节肌动蛋白丝滑动速度。
Smooth muscle myosin cross-bridge interactions modulate actin filament sliding velocity in vitro.
作者信息
Warshaw D M, Desrosiers J M, Work S S, Trybus K M
机构信息
Department of Physiology and Biophysics, University of Vermont, College of Medicine, Burlington 05405.
出版信息
J Cell Biol. 1990 Aug;111(2):453-63. doi: 10.1083/jcb.111.2.453.
Although it is generally believed that phosphorylation of the regulatory light chain of myosin is required before smooth muscle can develop force, it is not known if the overall degree of phosphorylation can also modulate the rate at which cross-bridges cycle. To address this question, an in vitro motility assay was used to observe the motion of single actin filaments interacting with smooth muscle myosin copolymers composed of varying ratios of phosphorylated and unphosphorylated myosin. The results suggest that unphosphorylated myosin acts as a load to slow down the rate at which actin is moved by the faster cycling phosphorylated cross-bridges. Myosin that was chemically modified to generate a noncycling analogue of the "weakly" bound conformation was similarly able to slow down phosphorylated myosin. The observed modulation of actin velocity as a function of copolymer composition can be accounted for by a model based on mechanical interactions between cross-bridges.
虽然人们普遍认为，在平滑肌能够产生力量之前，肌球蛋白调节轻链的磷酸化是必需的，但目前尚不清楚磷酸化的总体程度是否也能调节横桥循环的速率。为了解决这个问题，我们使用了一种体外运动分析方法，来观察单根肌动蛋白丝与由不同比例的磷酸化和未磷酸化肌球蛋白组成的平滑肌肌球蛋白共聚物相互作用时的运动。结果表明，未磷酸化的肌球蛋白起到一种负荷的作用，减缓了肌动蛋白被循环更快的磷酸化横桥移动的速率。经过化学修饰以产生“弱”结合构象的非循环类似物的肌球蛋白，同样能够减缓磷酸化肌球蛋白的作用。观察到的肌动蛋白速度随共聚物组成的变化，可以用一个基于横桥之间机械相互作用的模型来解释。
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