Department of Physics, University at Buffalo, Buffalo, NY, USA.
Proteins. 2011 Jul;79(7):2291-305. doi: 10.1002/prot.23055. Epub 2011 May 16.
To explore the structural basis of processive stepping of myosin V along filamentous actin, we have performed comprehensive modeling of its key conformational states and transitions with an unprecedented residue level of details. We have built structural models for a myosin V monomer complexed with filamentous actin at four biochemical states [adenosine diphosphate (ATP)-, adenosine diphosphate (ADP)-phosphate-, ADP-bound or nucleotide-free]. Then we have modeled a myosin V dimer (consisting of lead and rear head) at various two-head-bound states with nearly straight lever arms rotated by intramolecular strain. Next, we have performed transition pathway modeling to determine the most favorable sequence of transitions (namely, phosphate release at the lead head followed by ADP release at the rear head, while ADP release at the lead head is inhibited), which underlie the kinetic coordination between the two heads. Finally, we have used transition pathway modeling to reveal the order of structural changes during three key biochemical transitions (phosphate release at the lead head, ADP release and ATP binding at the rear head), which shed lights on the strain-dependence of the allosterically coupled motions at various stages of myosin V's work cycle. Our modeling results are in agreement with and offer structural insights to many results of kinetic, single-molecule and structural studies of myosin V.
为了探索肌球蛋白 V 沿丝状肌动蛋白进行连续运动的结构基础，我们采用前所未有的详细残基水平，对其关键构象状态和转变进行了全面建模。我们构建了肌球蛋白 V 单体与四种生化状态（腺苷二磷酸 (ADP)-、二磷酸腺苷 (ATP)-、磷酸化 ADP-、无核苷酸）下的丝状肌动蛋白复合物的结构模型。然后，我们构建了近直杠杆臂的双肌球蛋白 V 二聚体（由前导头和后导头组成）在各种双头结合状态下的模型，这些模型通过分子内应变旋转。接下来，我们进行了过渡途径建模，以确定最有利的转变序列（即前导头的磷酸释放，随后后导头的 ADP 释放，同时抑制前导头的 ADP 释放），这是两个头之间动力学协调的基础。最后，我们使用过渡途径建模来揭示三个关键生化转变（前导头的磷酸释放、ADP 释放和后导头的 ATP 结合）期间结构变化的顺序，这为肌球蛋白 V 工作循环各个阶段的变构偶联运动的应变依赖性提供了线索。我们的建模结果与肌球蛋白 V 的动力学、单分子和结构研究的许多结果一致，并提供了结构见解。
