Conformational change of the actomyosin complex drives the multiple stepping movement.
Actin-myosin (actomyosin) generates mechanical force by consuming ATP molecules. We apply the energy landscape perspective to address a controversial issue as to whether the myosin head moves with multiple steps after a single ATP hydrolysis or only a single mechanical event of the lever-arm swinging follows a single ATP hydrolysis. Here we propose a theoretical model in which the refolding of the partially unfolded actomyosin complex and the movement of the myosin head along the actin filament are coupled. A single ATP hydrolysis is followed by the formation of a high free-energy partially unfolded actomyosin complex, which then gradually refolds with a concomitant multiple stepping movement on the way to the lowest free-energy rigor state. The model quantitatively explains the single-molecular observation of the multiple stepping movement and is consistent with structural observations of the disorder in the actomyosin-binding process. The model also explains the observed variety in dwell time before each step, which is not accounted for by previous models, such as the lever-arm or ratchet models.
Terada
Tomoki P
TP
Graduate School of Human Informatics, Nagoya University, Nagoya 464-8601, Japan. terada@info.human.nagoya-u.ac.jp
Sasai
Masaki
M
Yomo
Tetsuya
T
D000199:Actins / Q000737:chemistry / Q000502:physiology; D000205:Actomyosin / Q000737:chemistry* / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008954:Models, Biological; D009010:Monte Carlo Method; D009119:Muscle Contraction / Q000502:physiology; D009218:Myosins / Q000737:chemistry / Q000502:physiology; D011487:Protein Conformation; D013816:Thermodynamics
D000199:Actins; D046911:Macromolecular Substances; D000255:Adenosine Triphosphate; D000205:Actomyosin; D009218:Myosins