ADP inhibition of myosin V ATPase activity
ADP inhibition of myosin V ATPase activity
复制标题
DOI：
10.1016/s0006-3495(00)76403-4
复制
发表时间：
2000-09-01
影响因子：
3.4
通讯作者：
Ostap, EM
中科院分区：
文献类型：
--
作者：
De la Cruz, EM;Sweeney, HL;Ostap, EM
肌球蛋白V的动力学机制备受关注，因为近期的证据表明，双头肌球蛋白V分子作为一种持续性马达发挥作用，即肌球蛋白V能够在肌动蛋白丝上移动多个马达催化循环而不解离。最近三篇评估单头肌球蛋白V动力学的文献就该机制，特别是循环的限速步骤，得出了不同的结论。一项研究（德拉·克鲁兹等人，1999年，《美国国家科学院院刊》96卷：13726 - 13731页）将ADP释放确定为限速步骤，并为肌球蛋白V的持续性提供了一种动力学解释。其他研究（特里巴斯等人，1999年，《生物化学杂志》274卷：27448 - 27456页；王等人，2000年，《生物化学杂志》275卷：4329 - 4335页）没有确定限速步骤，但得出结论认为不是ADP释放。我们展示了实验和模拟数据，表明这些报告中的不一致可能是由于稳态ATP酶速率测量的困难。在标准测定条件下，ADP与ATP竞争，导致对ATP酶速率的产物抑制。这在分析和解释肌球蛋白V以及可能其他具有高ADP亲和力的肌球蛋白家族成员的动力学方面带来了技术问题。
The kinetic mechanism of myosin V is of great interest because recent evidence indicates that the two-headed myosin V molecule functions as a processive motor, i.e., myosin V is capable of moving along an actin filament for many catalytic cycles of the motor without dissociating. Three recent publications assessing the kinetics of single-headed myosin V provide different conclusions regarding the mechanism, particularly the rate-limiting step of the cycle. One study (De La Cruz et al., 1999, Proc. Natl. Acad. Sci USA. 96:13726-13731) identifies ADP release as the rate-limiting step and provides a kinetic explanation for myosin V processivity. The others (Trybus et al., 1999, J. Biol. Chem. 274:27448-27456; Wang et al., 2000, J. Biol. Chem. 275:4329-4335) do not identify the rate-limiting step but conclude that it is not ADP release. We show experimental and simulated data demonstrating that the inconsistencies in the reports may be due to difficulties in the measurement of the steady-state ATPase rate. Under standard assay conditions, ADP competes with ATP, resulting in product inhibition of the ATPase rate. This presents technical problems in analyzing and interpreting the kinetics of myosin V and likely of other members of the myosin family with high ADP affinities.