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马达蛋白肌球蛋白-I分两步产生其工作冲程。

The motor protein myosin-I produces its working stroke in two steps.

作者信息

Veigel C, Coluccio L M, Jontes J D, Sparrow J C, Milligan R A, Molloy J E

机构信息

Department of Biology, University of York, UK.

出版信息

Nature. 1999 Apr 8;398(6727):530-3. doi: 10.1038/19104.

Abstract

Many types of cellular motility, including muscle contraction, are driven by the cyclical interaction of the motor protein myosin with actin filaments, coupled to the breakdown of ATP. It is thought that myosin binds to actin and then produces force and movement as it 'tilts' or 'rocks' into one or more subsequent, stable conformations. Here we use an optical-tweezers transducer to measure the mechanical transitions made by a single myosin head while it is attached to actin. We find that two members of the myosin-I family, rat liver myosin-I of relative molecular mass 130,000 (M(r) 130K) and chick intestinal brush-border myosin-I, produce movement in two distinct steps. The initial movement (of roughly 6 nanometres) is produced within 10 milliseconds of actomyosin binding, and the second step (of roughly 5.5 nanometres) occurs after a variable time delay. The duration of the period following the second step is also variable and depends on the concentration of ATP. At the highest time resolution possible (about 1 millisecond), we cannot detect this second step when studying the single-headed subfragment-1 of fast skeletal muscle myosin II. The slower kinetics of myosin-I have allowed us to observe the separate mechanical states that contribute to its working stroke.

摘要

包括肌肉收缩在内的多种细胞运动形式,是由马达蛋白肌球蛋白与肌动蛋白丝的周期性相互作用驱动的,这种相互作用与ATP的分解相偶联。据认为,肌球蛋白与肌动蛋白结合,然后当它“倾斜”或“摆动”成一个或多个随后的稳定构象时产生力和运动。在这里,我们使用光镊传感器来测量单个肌球蛋白头部附着在肌动蛋白上时所进行的机械转变。我们发现,肌球蛋白-I家族的两个成员,相对分子质量为130,000(M(r) 130K)的大鼠肝脏肌球蛋白-I和鸡肠道刷状缘肌球蛋白-I,以两个不同的步骤产生运动。最初的运动(约6纳米)在肌动球蛋白结合后的10毫秒内产生,第二步(约5.5纳米)在可变的时间延迟后发生。第二步之后的时间段持续时间也是可变的,并且取决于ATP的浓度。在可能的最高时间分辨率(约1毫秒)下,当研究快速骨骼肌肌球蛋白II的单头亚片段-1时,我们无法检测到这第二步。肌球蛋白-I较慢的动力学使我们能够观察到有助于其工作行程的不同机械状态。

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