The structure of the acto-myosin subfragment 1 complex: results of searches using data from electron microscopy and x-ray crystallography.
The structure of the acto-myosin subfragment 1 complex: results of searches using data from electron microscopy and x-ray crystallography.
复制标题
肌动球蛋白亚片段 1 复合物的结构：使用电子显微镜和 X 射线晶体学数据的搜索结果。
DOI：
10.1073/pnas.94.16.8533
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发表时间：
1997
影响因子：
11.1
通讯作者：
Morris,EP
中科院分区：
文献类型：
--
作者：
Mendelson,R;Morris,EP
关于肌球蛋白亚片段1（S1）在肌肉收缩中如何与肌动蛋白丝相互作用的猜测，建立在对这两种蛋白质的相对排列的了解之上。虽然存在S1和肌动蛋白的晶体学结构，以及acto-S1复合物（AS 1）的电子显微镜数据，但这种排列的建模迄今为止只能“通过眼睛”完成。在这里，我们报告使用定量方法获得的拟合AS 1结构，该方法更客观，更完整地利用数据。使用未失真的晶体学结果，最佳拟合的AS 1结构显示出显着差异，从视觉拟合。使用Holmeset等人的F-肌动蛋白模型产生最佳拟合。[Holmes，K. C.的方法，Popp，D.，Gebhard，W. & Kabsch，W.（1990）Nature（伦敦）347，44-49]。S1残基在AS 1接口，现在发现在一个更高的半径，以及轴向平移和旋转方位角。使用同源性搜索方法预测环结构，实现了使用S1加上晶体结构缺失的环的拟合。这些改进的拟合有利于这样一种安排，其中S1的50至20 kDa结构域连接处的环位于肌动蛋白的N末端附近。刚性体运动的较低的50-kDa的结构域，这进一步提高了适合，产生关闭的大50-kDa的结构域裂缝，并使保守的残基在较低的50-kDa的结构域到一个明显适当的方向与肌动蛋白的密切相互作用。这一发现支持了这样的想法，即在ATP酶循环结束时ATP与AS 1的结合通过改变S1的50 kDa裂缝的构象来破坏肌动蛋白结合位点。
Surmises of how myosin subfragment 1 (S1) interacts with actin filaments in muscle contraction rest upon knowing the relative arrangement of the two proteins. Although there exist crystallographic structures for both S1 and actin, as well as electron microscopy data for the acto–S1 complex (AS1), modeling of this arrangement has so far only been done “by eye.” Here we report fitted AS1 structures obtained using a quantitative method that is both more objective and makes more complete use of the data. Using undistorted crystallographic results, the best-fit AS1 structure shows significant differences from that obtained by visual fitting. The best fit is produced using the F-actin model of Holmeset al.[Holmes, K. C., Popp, D., Gebhard, W. & Kabsch, W. (1990)Nature (London)347, 44–49]. S1 residues at the AS1 interface are now found at a higher radius as well as being translated axially and rotated azimuthally. Fits using S1 plus loops missing from the crystal structure were achieved using a homology search method to predict loop structures. These improved fits favor an arrangement in which the loop at the 50- to 20-kDa domain junction of S1 is located near the N terminus of actin. Rigid-body movements of the lower 50-kDa domain, which further improve the fit, produce closure of the large 50-kDa domain cleft and bring conserved residues in the lower 50-kDa domain into an apparently appropriate orientation for close interaction with actin. This finding supports the idea that binding of ATP to AS1 at the end of the ATPase cycle disrupts the actin binding site by changing the conformation of the 50-kDa cleft of S1.