ROLE OF PHOSPHORYLATION AS A REGULATORY MECHANISM IN MUSCLE CONTRACTION

了解平滑肌的调节和机制 收缩和肌动蛋白和肌球蛋白如何在非肌肉细胞中相互作用，我们有 一直在使用各种肌球蛋白功能的测定。 其中之一， 运动性测定，包括可视化，在荧光 显微镜下，荧光标记的肌动蛋白丝在 表面覆盖着肌球蛋白分子。 这一运动是一个积极的 这一过程需要肌球蛋白和MgATP的存在。 的移动 肌动蛋白丝由平滑肌和非肌球蛋白几乎 完全依赖于肌球蛋白光对肌球蛋白磷酸化 链激酶 钙依赖性细丝调节系统 与肌钙蛋白-原肌球蛋白系统相似但不相同的是 可能存在于平滑肌和非肌肉细胞中。 一个这样 系统依赖于钙调素和钙调素。 我们已经证明， 系统能够通过肌球蛋白调节肌动蛋白的运动， 钙依赖的方式。 另一个系统涉及一个最近 描述了平滑肌蛋白，钙调蛋白，它也结合钙调蛋白。 钙调蛋白在体外也可以调节肌动蛋白的滑动。 平滑肌中其他肌动蛋白结合蛋白的功能 不被理解。 细丝蛋白是一种肌动蛋白捆绑蛋白。一个这样 example. 它大量存在于平滑肌组织中。 我们发现 细丝蛋白能够施加内部负荷， 在体外运动试验中，肌动蛋白被肌球蛋白主动滑动。

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 movement of fluorescently-labeled actin filaments over a surface coated with myosin molecules. This movement is an active process which requires the presence of myosin and MgATP. The movement of actin filaments by smooth muscle and nonmuscle myosins is almost completely dependent upon phosphorylation of the myosin by myosin light chain kinase. Calcium-dependent thin filament regulatory systems similar, but not identical, to the troponin-tropomyosin system are potentially present in smooth muscle and nonmuscle cells. One such system depends on caldesmon and calmodulin. We have shown that this system is capable of regulating the movement of actin by myosin in a calcium-dependent manner. Another system involves a more recently described smooth muscle protein, calponin, which also binds calmodulin. Calponin can also regulate the sliding of actin in vitro. The function of other actin binding proteins in smooth muscle is not understood. Filamin, an actin bundling protein, is. one such example. It exists in smooth muscle tissue in large quantities. We find that filamin is capable of exerting an internal load that is resistant to the active sliding of actin by myosin in the in vitro motility assay.