A comparison of contractile proteins from muscle and non-muscle systems



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A review of the literature dealing with contractile protein in muscle and non-muscle systems was done. Proteins resembling the major proteins of the muscle contractile system, actin and myosin, have been found in several types of non-muscle cells. These have been identified by their biochemical properties. Actin has the ability to form filaments and to interact with muscle myosin. Myosin possess actin-activatable enzymatic activity. Actin isolated from various sources appears to be identical to muscle actin in its functional properties, although there are minor differences in chemical composition and physical properties. In contrast with the actin myosin-like proteins which have been purified from primitive eucaryotic cells may differ from one another and muscle myosin in important characteristics. Chelating agents and SH reagents, such as ethylenediamine tetraacetate and PHMB, have been used extensively in the study of ATPase activity. A detailed discussion of SH groups which differ in susceptibility is presented for understanding myosin ATPase activity. Microtubules are important for some types of biological movement. Colchicine is a useful tool for the study of microtubules. Microfilaments are important for a wide variety of cellular movements by virtue of contractile activity via a sliding interaction with myosin. The chemical nature of cyto-chalagin B-aensltive microfilaments remains unkown. There is evidence that microfilaments are similar to actin filaments. Cytochalasin B inhibits a wide variety of cellular movements. The molecular mechanism which controls primitive cellular movement resembles the mechanism for control of muscle contraction. Comparisons of some isolated eucaryotic contractile proteins have produced several controversial hypotheses. One hypothesis is that the actin-myosin based contractile mechanism of muscle is a specialized example of a widely distributed fundamental mechanism of generating force for movement in all eucaryotic cells.