MODELLING THE INTERFACE BETWEEN ACTIN AND MYOSIN ON ACTIVE MUSCLE

该子项目是利用 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。 先前的工作者已经基于来自分离的蛋白质的组合晶体学和电子显微镜数据提出了肌球蛋白头在肌动蛋白上的对接的高分辨率模型（Mendelson和Morris，1997 PNAS 94：8533; Holmes等人，2003 Nature 425：423）。另一个研究小组还声称，力产生的第一步与肌球蛋白-肌动蛋白界面的重排有关，随后是杠杆臂倾斜，并且它是温度依赖性的（Ferenczi等人，2005 Structure 13：131）。这项工作的目标是收集小角X射线散射（SAXS）数据，肌肉，可用于检查在体内的预测模型的肌动蛋白-肌球蛋白对接，是否有一个温度依赖性重排的肌球蛋白-肌动蛋白接口。 为此，图案中最敏感的反射是由肌动蛋白单体沿着肌动蛋白丝的规则重复产生的2.73 nm的单光子反射，其在肌球蛋白附着于肌动蛋白时改变其强度。初步的模拟表明，反射强度的影响不大的杠杆臂倾斜，但它是高度敏感的相对轴向位置的肌动蛋白和肌球蛋白的催化域。将从静止时和在不同温度（4至17 ℃）下等长收缩期间的肌肉中获取2D图案，在倒易空间中高达0.5 nm-1，以收集基于肌动蛋白的2.73 nm的反射和5.9 nm和5.1 nm的层线，也受到肌球蛋白附着到肌动蛋白的影响。

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. Previous workers have proposed high resolution models for the docking of the myosin heads on actin on the basis of combined crystallographic and electron microscopy data from isolated proteins (Mendelson and Morris, 1997 PNAS 94:8533; Holmes et al. 2003 Nature 425:423). Another group also claims that the first step in the force generation is associated with a rearrangement of the myosin-actin interface, followed by the lever arm tilt, and that it is temperature-dependent (Ferenczi et al. 2005 Structure 13:131). The goal of this work is to collect small angle X-ray scattering (SAXS) data from muscle that may be used to check in vivo the prediction of the models for the acto-myosin docking and whether there is a temperature-dependent rearrangement of the myosin-actin interface. For this purpose, the most sensitive reflection in the pattern is the 2.73nm meridional reflection arising from the regular repeat of the actin monomers along the actin filament, which changes its intensity upon myosin attachment to actin. Preliminary modelling has shown that the reflection intensity is little influenced by the lever arm tilt but it is highly sensitive to the relative axial position of actin and catalytic domain of myosin. 2D patterns will be taken from muscle at rest and during isometric contraction at different temperatures (4 to 17¿C) up to 0.5 nm-1 in reciprocal space, in order to collect the actin-based 2.73nm meridional reflection and the 5.9nm and 5.1nm layer lines, also influenced by myosin attachment to actin.