Is myosin a "back door" enzyme?
Is myosin a "back door" enzyme?
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DOI：
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发表时间：
1995-04
影响因子：
3.4
通讯作者：
R. Yount;D. Lawson;I. Rayment
中科院分区：
文献类型：
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作者：
R. Yount;D. Lawson;I. Rayment
利用腺苷酸激酶将ATP模拟成鸡骨骼肌球蛋白亚片段-1的活性位点。Ap5A结构作为起始参考。由此产生的停靠ATP。S1结构是合理的，因为它使几个ATP类似物的光标记数据合理化。ATP的γ -磷酸位于活性位点口袋的底部，沿着S1突出的50 kda间隙部分可见，但从活性位点上方看则不可见。据推测，肌动蛋白结合促进p环和Arg-245的运动，使ATP的Pi通过50 kda片段的“后门”离开，而ADP仍然结合在活性位点。这种机制可以解释许多实验观察，包括ATP水解动力学，Pi交换成ATP的核苷酸依赖性，以及肌肉纤维中稳定的肌球蛋白。adp .钒酸盐复合物的形成。
ATP has been modeled into the active site of chicken skeletal myosin subfragment-1 using the adenylate kinase.Ap5A structure as a starting reference. The resulting docked ATP.S1 structure is justified in that it rationalizes the photolabeling data from several ATP analogs. The gamma-phosphate of ATP sits at the bottom of the active site pocket and is partially visible via a view along the prominent 50-kDa cleft of S1 but not when viewed from above the active site. It is postulated that actin binding promotes the movement of the P-loop and Arg-245 to allow Pi from ATP to leave via a "back-door" in the 50-kDa fragment while ADP is still bound at the active site. Such a mechanism can explain a number of experimental observations, including the kinetics of ATP hydrolysis, the nucleotide dependence of Pi exchange into ATP, and the formation of stable myosin.ADP.vanadate complexes in muscle fibers.