Lowey S, Trybus K M
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
Biophys J. 1995 Apr;68(4 Suppl):120S-126S; discussion 126S-127S.
A persistent problem with the rotating cross-bridge model for muscle contraction has been the inability to detect any large conformational changes within the myosin molecule to account for a working stroke of 5-10 nm. The recent crystal structure of myosin subfragment-1 suggests a solution to this problem by showing the presence of two distinct domains: a catalytic or motor domain, from which extends a long, 8.5-nm alpha-helix that is stabilized by the regulatory and essential light chains. Rayment et al. (1993) proposed that closure of a cleft in the motor domain could rotate the light chain-binding domain by a sufficient distance to account for the power stroke. With the development of new in vitro motility assays, and the ability to prepare unusual myosins by biochemical and molecular biological methods, we can now examine this hypothesis and explore the role of the light chains in generating force and movement. Here we will review some of these recent data and outline a possible mechanism for how light chains regulate contractile properties.
肌肉收缩的旋转横桥模型一直存在一个持久性问题，即无法检测到肌球蛋白分子内有任何大的构象变化来解释5至10纳米的工作行程。最近肌球蛋白亚片段-1的晶体结构通过显示存在两个不同的结构域，为这个问题提供了一个解决方案：一个催化或运动结构域，从该结构域延伸出一条由调节轻链和必需轻链稳定的8.5纳米长的α螺旋。雷门特等人（1993年）提出，运动结构域中一个裂缝的闭合可以使轻链结合结构域旋转足够的距离来解释动力冲程。随着新的体外运动测定法的发展，以及通过生化和分子生物学方法制备异常肌球蛋白的能力，我们现在可以检验这个假设，并探索轻链在产生力和运动中的作用。在这里，我们将回顾一些这些最新数据，并概述轻链调节收缩特性的可能机制。
