ROLE OF PHOSPHORYLATION AS A REGULATORY MECHANISM IN MUSCLE CONTRACTION

了解平滑肌收缩的调节和机制 以及肌动蛋白和肌球蛋白如何在非肌肉细胞中相互作用，我们一直在使用 肌球蛋白功能的各种测定。 其中之一，体外运动 分析，涉及可视化，在荧光显微镜， 荧光标记的肌动蛋白丝在细胞膜上的ATP依赖性运动 表面覆盖着肌球蛋白分子。 运动平稳， 非肌肉肌球蛋白依赖于调节光的磷酸化 链 未磷酸化的肌球蛋白不支持运动， 与肌动蛋白弱相互作用。 平滑肌和非肌肉肌球蛋白转位 肌动蛋白丝缓慢相比，骨骼肌肌球蛋白，反映 它们在数量上不同的动力学。 如果缓慢的循环平稳或 非肌肉肌球蛋白与更快循环的骨骼肌肌球蛋白混合， 复合速度由较慢的循环肌球蛋白支配。 有趣的是，非循环非磷酸化平滑肌和非肌肉肌球蛋白 也可以减缓更快的循环肌球蛋白，大概是通过创造一个 通过与肌动蛋白的弱相互作用来增加内部负荷。

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.