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Coupling of Lever Arm Swing and Biased Brownian Motion in Actomyosin
Figure 9
Illustration of a cycle of the suggested myosin II movement.
The myosin structure is schematically represented as a composite of S2 (green) and S1, which is further composed of motor domain (black oval) and lever arm (blue). Black lines represent the free-energy landscapes for the myosin motor domain. (A) Myosin with ADP and Pi binds weakly to actin at around 
. (B) After the release of ADP and Pi, myosin begins to move along the actin filament, showing the biased Brownian motion. (C) Myosin reaches the strong binding site at 
and turns into the rigor state. (D) After binding ATP, myosin detaches from the actin filament and goes through the recovery stroke, which should change the orientation of the motor domain. (E) The myosin searches for the next binding site on the actin filament through the swinging motion of S1 and S2. (F) Because of the tilted orientation of the motor domain, myosin tends to bind to the next binding site at 
. In this way, the recovery stroke shown in D plays a positive role in generating the net displacement of myosin via cycles of ATP reactions.
doi: https://doi.org/10.1371/journal.pcbi.1003552.g009