Actomyosin contractility depends on the load-dependent binding kinetics of myosin motors*

Within the cytoskeleton, myosin motor proteins consume chemical energy and generate mechanical work within the filamentous actin network essential for diverse cell functions like migration, division, and shape change. Myosin unbinding kinetics are force dependent- exhibiting “catch-bond” behavior which decreases the probability of unbinding under load. Altering the binding kinetics of proteins is prohibitively difficult, thus the impact of load dependent binding kinetics on the dynamics and mechanics of actomyosin contractility are unclear. To this end, we use coarse grained molecular dynamics simulations to explore the effect of catch bonds on the accumulation and dissipation of mechanical energy in the actomyosin cytoskeleton. We find that motor binding that increases under load sensitizes the network to myosin motor concentration, increasing the rate of contractility while simultaneously increasing network toughness, or the storage of mechanical energy.