ROLE OF WEAKLY BOUND CROSSBRIDGES IN MUSCLE CONTRACTION

人体肌肉系统包含三种肌肉类型：心肌， 骨骼肌用于身体稳定和运动， 脉管系统消化系统和生殖系统 了解 影响特定肌肉类型的疾病，有必要了解 这些肌肉的收缩和调节的机制， 收缩。 药物干预取决于 选择性地改变每种肌肉类型的收缩性。 为此我们 一直在研究平滑肌和平滑肌细胞收缩的调节， 横纹肌（心肌和骨骼肌）。 我们之前已经证明， 横纹肌的钙调节，通过蛋白质肌钙蛋白和 原肌球蛋白，不发生由肌球蛋白-ATP的结合减弱， 肌动蛋白原肌球蛋白肌钙蛋白 相反，在没有Ca 2+的情况下， 过程，大概是产品释放，被抑制。 相比之下， 已经表明，在肌球蛋白与肌动蛋白-原肌球蛋白-肌钙蛋白的结合中， 缺乏ATP，是Ca 2+依赖性的。 这些数据符合一个模型 肌球蛋白从弱结合的 状态（含有结合ATP或ADP + Pi）到强结合状态 （含有结合的ADP）。 这种转变不可能以显著的速度发生 除非肌动蛋白也从非活性状态转变为活性状态， 状态 我们现在建议使用多学科的方法来测试这一点 假设，并进一步表征行动和 肌球蛋白 我们已经证明平滑肌蛋白caldesmon， 抑制肌球蛋白-ATP与肌动蛋白的结合。 这种蛋白质是一种极好的 肌球蛋白桥结合探针，可用于研究肌球蛋白的功能 肌球蛋白的弱结合状态。 我们将使用绑定研究， 停流动力学研究，以研究弱结合的性质 肌球蛋白桥。 这些生化研究将伴随着 机械和X射线衍射测量单个肌肉纤维， 确定弱约束的跨桥在收缩中的重要性， 调控 我们还将使用肌纤维模型来研究可能的 钙调素和一种新发现的蛋白质钙调蛋白的调节作用。 最后，我们将详细研究 caldesmon和一种新发现的蛋白质calponin。 最后，我们将 一个详细的研究结合的肌球蛋白肌动蛋白在存在的 ATPgammaS测试最近的挑战，我们的假设，调节 横纹肌发生在从弱结合状态过渡到 强大的十字桥国家。

The human muscle system contains three muscle types: cardiac muscle, skeletal muscle for physical stability and movement, and smooth muscle in the vasculature, digestive, and reproductive systems. To understand disorders affecting particular muscle types it is necessary to understand mechanisms both of contraction of these muscles and of regulation of contraction. Pharmacologic intervention depends on the ability to selectively modify the contractility of each muscle type. To this end we have been studying the regulation of contraction of both smooth and striated (cardiac and skeletal) muscles. We have shown earlier that the Ca2+ regulation of striated muscle, through the proteins troponin and tropomyosin, does not occur by a weakening of the binding of myosin-ATP to actin-tropomyosin-troponin. Rather, in the absence of Ca2+, the rate of a process, presumably product release, is inhibited. In contrast, it has been shown that the binding of myosin to actin-tropomyosin-troponin, in the absence of ATP, is Ca2+ dependent. These data are consistent with a model of contraction where both myosin makes the transition from a weakly bound state (containing bound ATP or ADP + Pi) to a strongly bound state (containing bound ADP). This transition cannot occur at a significant rate unless actin also makes a transition from the inactive state to the active state. We now propose to use a multidisciplinary approach to test this hypothesis and to further characterize the duality of states of actin and myosin. We have shown that the smooth muscle protein, caldesmon, does inhibit the binding of myosin-ATP to actin. This protein is an excellent probe of myosin crossbridge binding and can be used to study the function of the weakly bound state of myosin. We will use binding studies and stopped-flow kinetic studies to investigate the properties of weakly bound myosin crossbridges. These biochemical studies will be accompanied by mechanical and X-ray diffraction measurements of single muscle fibers to determine the importance of weakly bound crossbridges in contraction and in regulation. We will also use the muscle fiber model to study possible regulatory roles of caldesmon and a newly discovered protein, calponin. Finally, we will make a detailed study possible regulatory roles of caldesmon and a newly discovered protein, calponin. Finally, we will make a detailed study of the binding of myosin to actin in the presence of ATPgammaS to test a recent challenge to our hypothesis that regulation of striated muscle occurs at the transition from the weak binding states to the strong crossbridge states.