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Chemomechanical regulation of myosin Ic cross-bridges: Deducing the elastic properties of an ensemble from single-molecule mechanisms
Fig 6
Ensemble of coupled myosin heads.
(a) A simplified ensemble model for determining the average number of myosin heads bound to the actin filament. Each of the N myosin heads can either bind to the filament with binding rate kon or unbind with unbinding rate koff. The system can be described as a finite Markov chain in which each state is associated with the number of bound myosin heads. The transition rates 
and 
between these states are effective rates that depend on the number n of bound myosin heads. (b) The average number of bound myosin heads for an ensemble of N = 30 myosin molecules for a cooperative model (blue, solid line) in which the force per molecule f = F/n is the total external force F divided by the number n of bound myosin heads. In the two non-cooperative models (red and yellow solid lines) the force per molecule is either constant, f = F/N, or varies according to 
, in which 
is an estimated average number of bound motors. The results of a full Monte Carlo simulation of 30 elastically coupled myosin heads are shown as the broken lines for two different coupling stiffnesses: κ = 200 μN/m (orange, broken line) and κ = 500 μN/m (green, broken line).
doi: https://doi.org/10.1371/journal.pcbi.1005566.g006