Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany; Centre for Structural Systems Biology (CSSB), German Electron Synchrotron (DESY), Hamburg, Germany.
Cytoskeleton (Hoboken). 2013 Oct;70(10):651-60. doi: 10.1002/cm.21125. Epub 2013 Aug 13.
We propose that on binding to actin at the start of the power stroke the myosin cross-bridge takes on the rigor configuration at the actin interface. Starting from the prepower stroke state, this can be achieved by a small movement (16° rotation) of the lower 50K domain without twisting the central β-sheet or opening switch-1 or switch-2. The movement of the lower 50K domain puts a strain on the W-helix. This strain tries to twist the β-sheet, which could drive the power stroke. This would provide a coupling between actin binding and the execution of the power stroke. During the power stroke the β-sheet twists, moving the P-loop away from switch-2, which opens the nucleotide binding pocket and separates ADP from Pi . The power stroke is different from the recovery stroke because the upper and lower 50K domains are tethered in the rigor configuration.
我们提出，在动力冲程开始时，肌球蛋白与肌动蛋白结合，在肌动蛋白界面上形成僵硬构象。从预备动力冲程状态开始，可以通过小幅度移动（16°旋转）下部 50K 结构域来实现，而不扭转中心β-片层或打开开关-1 或开关-2。下部 50K 结构域的移动对 W 螺旋施加了应变。这种应变试图扭曲β-片层，从而可以驱动动力冲程。这将在肌动蛋白结合和动力冲程的执行之间提供一种耦合。在动力冲程中，β-片层扭曲，使 P 环远离开关-2，从而打开核苷酸结合口袋并使 ADP 与 Pi 分离。动力冲程与恢复冲程不同，因为上下 50K 结构域在僵硬构象中被束缚。
