Myosin structure

Figure 1. An unrooted phylogenetic tree of the myosins based on the amino acid sequence comparison of their head domains demonstrating the division of the myosin superfamily into nine classes. The lengths of the branches are proportional to the percent of amino acid sequence divergence and a calibration bar for 5% sequence divergence is shovk n. The different classes of myosins have been numbered using Roman numerals in rough order of their discovery and hypothetical models of the different myosin structures are shown. Question marks indicate either hypothetical or unknown structural features, and only a fraction of the known myosins are shown. (Taken, in modified form, from Cheney et al., 1993).

B. Paterson and R. C. Strohman, Biochemistry, 9 4094-4105 (1970). Myosin Structure as Revealed by Simultaneous Electrophoresis of Heavy and Light Subunits. 

Figure 34.2. Myosin Structure at Low Resolution. Electron micrographs of myosin molecules reveal a two-headed structure with a long, thin tail. [Courtesy of Dr. Paula Flicker, Dr. Theo Walliman, and Dr. Peter Vihert.]...

Figure 34.4. Myosin Structure at High Resolution. The structure of the SI fragment from muscle myosin reveals the presence of a P-loop NTPase domain (shaded in purple). An a helix that extends from this domain is the binding site for the two light chains.

There is an important difference between the macroscopic actin/myosin structure in muscle cells discussed above and the separate actin/myosin threads involved in the locomotion of individual cells. This form of myosin (myosin I) is also quite different, with one head instead of two as in muscle cells (myosin II), further it lacks a tail. Another interesting property of myosin I is its membrane... 

Adelstein RS, Sellers JR (1996) Myosin structure and function. In Barany M (ed) Biochemistry of Smooth Muscle Contraction. Academic Press Inc. San Diego, California, pp 3-19... 

Warrick HM, Spudich JA (1987) Myosin structure and function in cell motility. Annu Rev Cell Biol 3 379421... 

Citi S. and Kendrick-Jones J. 1987. Regulation of non-muscle myosin structure and function. Bioessays 1 155-159. 

Myosin ATPase. For some time the close association of ATPase and myosin in muscle has suggested an interaction of ATP breakdown with a concomitant change in the myosin structure. Well-washed myosin will consistently catalyze the cleavage of ATP — ADP + Pi with a pronounced reduction in the asymmetry of the myosin particles. 

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