The motor domain determines the large step of myosin-V
The motor domain determines the large step of myosin-V
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DOI：
10.1038/415192a
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发表时间：
2002-01-10
期刊：
影响因子：
64.8
通讯作者：
Ikebe, M
中科院分区：
文献类型：
--
作者：
Tanaka, H;Homma, K;Ikebe, M
V类肌球蛋白沿着肌动蛋白细丝以较大(类似36 nm)的步长(1-3)前进。肌球蛋白V有两个头部，每个头部由一个运动区和一个长(23 Nm)的颈区组成。根据被广泛接受的杠杆-手臂模型(4)，有人认为肌球蛋白-V通过倾斜其长颈(杠杆-手臂)(5)，沿着肌动蛋白螺旋重复序列步入连续的(36 Nm)靶区。为了验证这一假设，我们测量了颈区仅为天然长度六分之一的肌球蛋白V截断突变体的单分子的机械性能。我们的结果表明，肌动蛋白的加工速度和步长都与全长肌球蛋白V相似。因此，无论是大步还是肌球蛋白-V的加工能力，长颈结构域都不是必不可少的。这些结果挑战了杠杆-手臂模型。我们认为，运动结构域和/或肌动球蛋白界面使肌球蛋白-V在肌动蛋白转位过程中产生大的过程台阶。
Class-V myosin proceeds along actin filaments with large (similar to 36 nm) steps(1-3). Myosin-V has two heads, each of which consists of a motor domain and a long (23 nm) neck domain. In accordance with the widely accepted lever-arm model(4), it was suggested that myosin-V steps to successive (36 nm) target zones along the actin helical repeat by tilting its long neck (lever-arm)(5). To test this hypothesis, we measured the mechanical properties of single molecules of myosin-V truncation mutants with neck domains only one-sixth of the native length. Our results show that the processivity and step distance along actin are both similar to those of full-length myosin-V. Thus, the long neck domain is not essential for either the large steps or processivity of myosin-V. These results challenge the lever-arm model. We propose that the motor domain and/or the actomyosin interface enable myosin-V to produce large processive steps during translocation along actin.