The Fundamental Molecular Event in Muscular Contraction

Abstract

ASTBURY^{1 2} suggested that the fundamental event in the contraction of muscle might involve a characteristic of the keratin–myosin–epidermin–fibrinogen group of fibrous proteins to which myosin belongs, namely, the folding or collapsing of polypeptide chains from the α-configuration into the supercontracted state. While it has been shown that isolated myosin and actomyosin supercontracts after reasonably mild chemical or physical treatment^2,3, no X-ray evidence has been forthcoming so far to show that the shrinkage of actomyosin gels after treatment with adenosine triphosphate is accompanied by a corresponding configurational change⁴. Moreover, there is the difficulty of reconciling this approach with recent concepts of a two-phase actin–myosin system shortening by close-range⁵ or long-range⁶ interaction of filaments coiling or sliding over one another in a regular stepwise fashion.