Oscillatory Behavior in Muscle Myosin

Abstract

Muscle contraction is generated by cyclical interactions of myosin heads with actin filaments to form the actomyosin complex. The stable configurations of the actomyosin complex have been described in detail, but whether the in vivo configurations at physiological temperatures are fixed to those observed in cryomicroscopy (at low temperature) or undergo thermal oscillations is unknown and not generally considered in mathematical modeling.By comparing three mathematical models, we analyze whether thermal oscillations of the actomyosin complex affect muscle contraction at three levels; namely, single cross-bridge, single fiber and organ levels, in a textit{ceteris paribus} analysis.We observed that state fluctuations allow the lever arm of myosin to easily and dynamically explore all possible minima in the energy landscape, generating several backward and forward jumps between states during the lifetime of the actomyosin complex, whereas the rigid case is characterized by fewer force generating events. Therefore, dynamical oscillations enable an efficient contraction mechanism, in which a higher force is sustained by fewer attached cross-bridges.