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Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient
Osaka University, 1-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
Faculty of Engineering, Hokkai-Gakuen University, S26 W11, Chuo-ku, Sapporo, 064-0926, Japan
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641, Yamazaki, Noda, Chiba, 278-8510, Japan
* Author to whom correspondence should be addressed.
Received: 19 December 2010; in revised form: 20 February 2011 / Accepted: 22 February 2011 / Published: 4 March 2011
Abstract: Mitsui and Ohshima (2008) criticized the power-stroke model for muscle contraction and proposed a new model. In the new model, about 41% of the myosin heads are bound to actin filaments, and each bound head forms a complex MA3 with three actin molecules A1, A2 and A3 forming the crossbridge. The complex translates along the actin filament cooperating with each other. The new model well explained the experimental data on the steady filament sliding. As an extension of the study, the isometric tension transient and isotonic velocity transient are investigated. Statistical ensemble of crossbridges is introduced, and variation of the binding probability of myosin head to A1 is considered. When the binding probability to A1 is zero, the Hill-type force-velocity relation is resulted in. When the binding probability to A1 becomes finite, the deviation from the Hill-type force-velocity relation takes place, as observed by Edman (1988). The characteristics of the isometric tension transient observed by Ford, Huxley and Simmons (1977) and of the isotonic velocity transient observed by Civan and Podolsky (1966) are theoretically reproduced. Ratios of the extensibility are estimated as 0.22 for the crossbridge, 0.26 for the myosin filament and 0.52 for the actin filament, in consistency with the values determined by X-ray diffraction by Wakabayashi et al. (1994).
Keywords: muscle contraction mechanism; theory; isometric tension transient; isotonic velocity transient; double-hyperbolic force-velocity relation; crossbridge extensibility; filament extensibility; actomyosin complex; U* transition; U*12 transition
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Mitsui, T.; Takai, N.; Ohshima, H. Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient. Int. J. Mol. Sci. 2011, 12, 1697-1726.
Mitsui T, Takai N, Ohshima H. Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient. International Journal of Molecular Sciences. 2011; 12(3):1697-1726.
Mitsui, Toshio; Takai, Nobukatsu; Ohshima, Hiroyuki. 2011. "Remarks on Muscle Contraction Mechanism II. Isometric Tension Transient and Isotonic Velocity Transient." Int. J. Mol. Sci. 12, no. 3: 1697-1726.