Harada Y, Noguchi A, Kishino A, Yanagida T
Nature. 1987;326(6115):805-8. doi: 10.1038/326805a0.
The myosin molecule consists of two heads, each of which contains an enzymatic active site and an actin-binding site. The fundamental problem of whether the two heads function independently or cooperatively during muscle contraction has been studied by methods using an actomyosin thread, superprecipitation and chemical modification of muscle fibres. No clear conclusion has yet been reached. We have approached this question using an assay system in which sliding movements of fluorescently labelled single actin filaments along myosin filaments can be observed directly. Here, we report direct measurement of the sliding of single actin filaments along one-headed myosin filaments in which the density of heads was varied over a wide range. Our results show that cooperative interaction between the two heads of myosin is not essential for inducing the sliding movement of actin filaments.
肌球蛋白分子由两个头部组成，每个头部都包含一个酶活性位点和一个肌动蛋白结合位点。关于在肌肉收缩过程中这两个头部是独立发挥作用还是协同发挥作用这一基本问题，人们已经通过使用肌动球蛋白丝、超沉淀以及对肌肉纤维进行化学修饰等方法进行了研究。但尚未得出明确结论。我们采用了一种检测系统来探讨这个问题，在该系统中可以直接观察到荧光标记的单根肌动蛋白丝沿着肌球蛋白丝的滑动运动。在此，我们报告了对单根肌动蛋白丝沿着单头肌球蛋白丝滑动的直接测量，其中头部密度在很宽的范围内变化。我们的结果表明，肌球蛋白的两个头部之间的协同相互作用对于诱导肌动蛋白丝的滑动运动并非必不可少。
