ROLE OF PHOSPHORYLATION AS A REGULATORY MECHANISM IN MUSCLE CONTRACTION

了解平滑肌收缩的规律和机制 以及肌动蛋白和肌球蛋白在非肌肉细胞中的相互作用，我们一直在使用 肌球蛋白功能的各种分析。其中之一，体外运动性 化验，涉及在荧光显微镜下的可视化， 依赖于ATP的荧光标记的肌动蛋白细丝在 表面涂有肌球蛋白分子。顺畅和顺畅的运动 非肌肉肌球蛋白依赖于调节光的磷酸化 链条。未磷酸化的肌球蛋白不支持运动，但支持运动 与肌动蛋白的相互作用很弱。平滑和非肌肉肌球蛋白易位 肌动蛋白细丝比骨骼肌肌球蛋白慢，反映 它们在数量上的不同动力学。如果缓慢的骑行顺利或 非肌肉肌球蛋白与循环速度更快的骨骼肌肌球蛋白混合， 复合速度主要由循环速度较慢的肌球蛋白决定。 有趣的是，非周期非磷酸化的平滑和非肌肉肌球蛋白 也可以减缓更快的肌球蛋白循环，可能是通过创建一个 通过其与肌动蛋白的弱相互作用而产生的内部负荷。

To understand the regulation and mechanism of smooth muscle contraction and how actin and myosin interact in nonmuscle cells, we have been using various assays of myosin function. One of these, the in vitro motility assay, involves the visualization, in the fluorescent microscope, of the ATP-dependent movement of fluorescently-labeled actin filaments over a surface coated with myosin molecules. The movement of both smooth and nonmuscle myosin is dependent on phosphorylation of the regulatory light chain. Unphosphorylated myosin does not support movement, but does interact weakly with actin. Smooth and nonmuscle myosins translocate actin filaments slowly compared to skeletal muscle myosin, reflecting their quantitively different kinetics. If the slowly cycling smooth or nonmuscle myosin is mixed with the faster cycling skeletal muscle myosin, the composite velocity is dominated by the slower cycling myosin. Interestingly, the noncycling unphosphorylated smooth and nonmuscle myosin can also slow the faster cycling myosins, presumably by creating an internal load through its weak interactions with actin.