Functional role of loop 2 in myosin V.
Functional role of loop 2 in myosin V.
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环 2 在肌球蛋白 V 中的功能作用。
DOI：
10.1021/bi035510v
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Sweeney,HLee
中科院分区：
文献类型：
--
作者：
Yengo,ChristopherM;Sweeney,HLee
肌凝蛋白V是一种分子马达，能够沿着肌动蛋白丝进行运动。含有单个IQ结构域（MV 1IQ）的单体肌凝蛋白V的动力学与非进程性肌凝蛋白II的不同之处在于，肌动蛋白亲和力更高，磷酸盐释放极快，ADP释放有限速。我们通过改变环2（肌动蛋白结合区域的一个表面环，被认为改变肌动蛋白亲和力和肌动蛋白II中的磷酸盐释放）产生了两个肌凝蛋白V突变体，以确定该环在肌凝蛋白V的动力学调节中所起的作用。环2突变体改变了肌动蛋白（KATPase）的表观亲和力，但没有改变最大atp酶速率（VMAX）。瞬态动力学分析表明，与肌动蛋白的结合速率以及对肌动蛋白的亲和力取决于环2的净正电荷，而atp酶循环中的其他步骤不变。磷酸的最大释放速率没有变化，但对肌动蛋白在M·ADP·pi状态的亲和力被环2突变显著改变。因此，环2对于允许肌凝蛋白V在弱结合状态下以相对高的亲和力与肌动蛋白结合很重要，但在产物释放步骤中不起直接作用。在弱结合状态下对肌动蛋白保持高亲和力的能力可能会阻止肌动蛋白远离丝的扩散，并增加肌凝蛋白V的进展运动程度。
Myosin V is molecular motor that is capable of moving processively along actin filaments. The kinetics of monomeric myosin V containing a single IQ domain (MV 1IQ) differ from nonprocessive myosin II in that actin affinity is higher, phosphate release is extremely rapid, and ADP release is rate-limiting. We generated two mutants of myosin V by altering loop 2, a surface loop in the actin-binding region thought to alter actin affinity and phosphate release in myosin II, to determine the role that this loop plays in the kinetic tuning of myosin V. The loop 2 mutants altered the apparent affinity for actin (KATPase) without altering the maximum ATPase rate (VMAX). Transient kinetic analysis determined that the rate of binding to actin, as well as the affinity for actin, was dependent on the net positive charge of loop 2, while other steps in the ATPase cycle were unchanged. The maximum rate of phosphate release was unchanged, but the affinity for actin in the M·ADP·Pi-state was dramatically altered by the mutations in loop 2. Thus, loop 2 is important for allowing myosin V to bind to actin with a relatively high affinity in the weak binding states but does not play a direct role in the product release steps. The ability to maintain a high affinity for actin in the weak binding states may prevent diffusion away from the actin filament and increase the degree of processive motion of myosin V.
(±)-Scandine的合成研究
DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
林佑次郎
通讯作者：
林佑次郎