X-RAY INTERFERENCE STUDIES OF TROPONIN MOVEMENTS DURING MUSCLE ACTIVATION

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 研究中心，而研究中心不一定是研究者所在的机构。 脊椎动物的骨骼肌是通过钙离子与调节蛋白肌钙蛋白结合而启动的，肌钙蛋白是含肌动蛋白的肌丝中复合物的一部分，在收缩过程中，肌丝会主动滑过肌球蛋白。这种结合改变了第二种调节蛋白原肌球蛋白的位置，原肌球蛋白控制肌球蛋白跨桥与下面的肌动蛋白丝的连接，从而使张力发展。 已经确定，原肌球蛋白在激活过程中改变其在肌动蛋白上的方位角位置，但这是如何发生的目前还不清楚。肌钙蛋白的高分辨率晶体结构最近已经解决，这表明该结构的一部分可能经历倾斜运动以移动原肌球蛋白。这可能表现为肌钙蛋白质心轴向位置的微小变化，可以通过研究肌钙蛋白沿着肌动蛋白丝轴向重复的385 A构象反射的干涉精细结构来测量。这种精细结构是由Z线两侧的肌动蛋白丝对称定位产生的，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。 我们已经有相当成功的经验，应用这项技术来测量肌肉收缩过程中肌球蛋白横桥的详细行为（见所附出版物）。我们现在需要更多的数据，以便对这一现象有一个令人信服的了解，并以时间分辨的方式对其进行研究，以便将这些变化联系起来

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 binding 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, allowing tension development. It is well-established that tropomyosin changes its azimuthal position on actin during activation, but how this is brought about is at present unknown. The high-resolution crystallographic structure of troponin has been solved recently, suggesting 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 that 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. We have already had considerable successful experience in applying this technique to measurements of the detailed behavior of myosin crossbridges during muscle contraction (see attached publications). We now need considerably more data, to obtain a convincing picture of the phenomenon and to study it in a time-resolved manner, so as to correlate the changes