Elastic lever-arm model for myosin V
Elastic lever-arm model for myosin V
复制标题
DOI：
10.1529/biophysj.104.046763
复制
发表时间：
2005-06-01
影响因子：
3.4
通讯作者：
Vilfan, A
中科院分区：
文献类型：
--
作者：
Vilfan, A
我们提出了一个机械化学模型的肌球蛋白V，一个双头进行马达蛋白。我们从一个单独的头部，我们都与四态循环模型（分离，连接ADP的二聚体的属性。Pi;附ADP;并且没有核苷酸连接），或者具有五态循环（其中动力冲程不与磷酸盐释放紧密耦合）。在每种状态下，杠杆臂以不同但固定的角度离开头部。杠杆臂本身被描述为弹性杆。两个头部的化学循环仅通过两个杠杆臂之间的机械连接来协调。该模型解释了头部协调显示，铅头只绑定到肌动蛋白后，在trail头的powerstroke，它只经历了它的powerstroke后，trail头unbinds从肌动蛋白。这两个模型（四和五状态）再现所观察到的手在手上的运动，并适合测得的力-速度关系。这两个模型之间的主要区别在于运行长度对负载的依赖性，这在五态模型中要弱得多。我们展示了如何在不同条件下系统的持续合成能力测量可以用来区分这两种模型，并确定动力学参数。
We present a mechanochemical model for myosin V, a two-headed processive motor protein. We derive the properties of a dimer from those of an individual head, which we model both with a four-state cycle ( detached; attached with ADP. Pi; attached with ADP; and attached without nucleotide) and alternatively with a five-state cycle ( where the powerstroke is not tightly coupled to the phosphate release). In each state the lever arm leaves the head at a different, but fixed, angle. The lever arm itself is described as an elastic rod. The chemical cycles of both heads are coordinated exclusively by the mechanical connection between the two lever arms. The model explains head coordination by showing that the lead head only binds to actin after the powerstroke in the trail head and that it only undergoes its powerstroke after the trail head unbinds from actin. Both models (four- and five-state) reproduce the observed hand-over-hand motion and fit the measured force-velocity relations. The main difference between the two models concerns the load dependence of the run length, which is much weaker in the five-state model. We show how systematic processivity measurement under varying conditions could be used to distinguish between both models and to determine the kinetic parameters.