X-RAY INTERFERENCE STUDIES OF TROPONIN MOVEMENTS DURING MUSCLE ACTIVATION

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 脊椎动物骨骼肌是通过肌肉中储存部位释放的钙离子的作用而启动的。钙与肌钙蛋白结合，肌钙蛋白是肌动蛋白微丝中一个复合体的一部分，在收缩过程中会主动滑过肌球蛋白细丝。这种结合改变了第二种调节蛋白原肌球蛋白的位置，它控制着肌球蛋白交叉连接到潜在肌动蛋白细丝的通道，这是张力发育所必需的。 原肌球蛋白在激活过程中会改变其在肌动蛋白上的方位，这一点已经得到了充分的证实，但目前还不清楚这是如何发生的。然而，肌钙蛋白的高分辨率晶体结构最近已经被解决，有迹象表明，该结构的一部分可能经历倾斜运动来移动原肌球蛋白。这可能表现为肌钙蛋白质心的轴向位置发生微小变化。这些可以通过研究肌钙蛋白沿肌动蛋白细丝的轴向重复的385A经向反射的干涉精细结构来测量。这种精细结构是通过在Z线两侧对称定位肌动蛋白细丝而产生的，这种精细结构的变化使人们能够以亚纳米精度测量轴向位置的变化。其目的是以时间分辨的方式研究这一现象，以便将肌肉激活过程中轴向位置的变化与其他事件联系起来。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Vertebrate skeletal muscle is switched on by the action of calcium ions released from storage sites in the muscle. Calcium binds to the regulatory protein troponin, part of a complex in the actin-containing filaments that actively slide past the myosin filaments during contraction.This binding alters the position of the second regulatory protein tropomyosin, which controls access of the myosin crossbridges to the underlying actin filaments, necessary for tension development. It is already well-established that tropomyosin changes its azimuthal position on actin during activation, but how this is brought about is at present unknown. However, the high-resolution crystallographic structure of troponin has been solved recently, and there are suggestions that part of that structure could undergo a tilting movement to move tropomyosin. This might show up as small changes in the axial position of the center of mass of troponin. These could be measured by studying the interference fine structure of the 385A meridional reflections from the axial repeat of troponin along actin filaments. This fine structure is generated by symmetrical positioning of actin filaments on either side of the Z-lines, and changes in such fine structure enable one to measure changes in axial position with sub-nanometer accuracy. The goal is to study this phenomenon in a time-resolved manner, so as to correlate the changes in axial position with other events during activation of muscle.