Umemoto S, Sellers J R
Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
J Biol Chem. 1990 Sep 5;265(25):14864-9.
We have used two in vitro motility assays to study the relative movement of actin and myosin from turkey gizzards (smooth muscle) and human platelets. In the Nitella-based in vitro motility assay, myosin-coated polymer beads move over a fixed substratum of actin bundles derived from dissection of the alga, Nitella, whereas in the sliding actin filament assay fluorescently labeled actin filaments slide over myosin molecules adhered to a glass surface. Both assay systems yielded similar relative velocities using smooth muscle myosin and actin under our standard conditions. We have studied the effects of ATP, ionic strength, magnesium, and tropomyosin on the velocity and found that with the exception of the dependence on MgCl2, the two assays gave very similar results. Calcium over a concentration of pCa 8 to 4 had no effect on the velocity of actin filaments. Phosphorylated smooth muscle myosin propelled filaments of smooth muscle and skeletal muscle actin at the same rate. Phosphorylated smooth muscle and cytoplasmic myosin monomers also moved actin filaments, demonstrating that filament formation is not required for movement.
我们使用了两种体外运动分析方法来研究来自火鸡砂囊（平滑肌）和人类血小板的肌动蛋白和肌球蛋白的相对运动。在基于丽藻的体外运动分析中，包被有肌球蛋白的聚合物珠在由藻类丽藻解剖得到的肌动蛋白束固定基质上移动，而在肌动蛋白丝滑动分析中，荧光标记的肌动蛋白丝在附着于玻璃表面的肌球蛋白分子上滑动。在我们的标准条件下，使用平滑肌肌球蛋白和肌动蛋白时，两种分析系统产生了相似的相对速度。我们研究了ATP、离子强度、镁和原肌球蛋白对速度的影响，发现除了对MgCl2的依赖性外，两种分析给出了非常相似的结果。钙离子浓度在pCa 8至4范围内对肌动蛋白丝的速度没有影响。磷酸化的平滑肌肌球蛋白以相同速率推动平滑肌和骨骼肌肌动蛋白丝。磷酸化的平滑肌和细胞质肌球蛋白单体也能移动肌动蛋白丝，表明运动不需要形成丝。
