The myosin power stroke

Abstract

Optical trapping technology now allows investigators in the motility field to measure the forces generated by single motor molecules. A handful of research groups have exploited this approach to further develop our understanding of the actin-based motor, myosin, an ATPase that is capable of converting chemical energy into mechanical work during a cyclical interaction with filamentous actin. In this regard, myosin-II from muscle is the most well-characterized myosin superfamily member. By combining the data obtained from optical trap assays with that from ensemble biochemical and mechanical assays, this review discusses the fundamental properties of the myosin-II power stroke and, perhaps more significantly, how these properties are governed by this molecule's atomic structure and the biochemical transitions that define its catalytic cycle. Cell Motil. Cytoskeleton 51:1-15, 2002.

Cardiac myosin binding protein-C modulates actomyosin binding and kinetics in the in vitro motility assay

“…If cMyBP-C decreases the rate of cross-bridge detachment as suggested above this would result in an increased cross-bridge attachment time [47]. A determinant of isometric force is the duty ratio, defined as the myosin attachment time divided by the total cycle time (i.e., time of the ATP hydrolysis cycle).…”

“…Thus, cMyBP-C, presumably through its interaction with the thin filament, modulates either the inherent mechanics and/or kinetics of the myosin cross-bridge [22]. Specifically, cMyBP-C could reduce the displacement generated by the myosin motor and/or the rate at which the cross-bridge detaches from actin following the powerstroke, both of which govern actin filament velocity at the molecular level [47]. Evidence for a kinetic effect already exists given that MyBP-C slows the rate of actomyosin ATP hydrolysis [48,49] and is consistent with a slower cross-bridge detachment rate being the most likely effect of cMyBP-C on thin filament velocity.…”

Coupling of Transverse and Longitudinal Response in Stiff Polymers

“…16 /7 and t L ≈ 0.2 s/f ⊥ [ pN] for (unstretched) actin filaments of about 20 µm length [4], which implies that the actin response to myosin motors becomes nonlinear on time scales comparable to the duration of a single power stroke [15]. Filaments in actin networks (mesh size ξ ≈ 1 10 L ≈ 0.5 µm) under stresses of about 1 Pa [11] are usually so short that t f ≫ t L ≈ 10 −4 s, but the coupling nonlinearity should be observable in the viscoelastic response [3].…”

Modification of Interface between Regulatory and Essential Light Chains Hampers Phosphorylation-dependent Activation of Smooth Muscle Myosin

“…Using a detachment-limited model, V ϭ d/T on , where V is velocity; d is the working stroke distance; and T on is the time in the ATPase cycle where cross-bridges are attached to actin. At high ATP, T on is inversely proportional to k ϪAD (28). This suggests that the observed actin sliding velocities for these mutants are slowed by some other factor.…”

“…Also, a more flexible lever arm could lead to a shorter working stroke, but we have no direct evidence for this as yet. It is known that the working stroke distance (d) is a mechanical property that depends upon the effective length of the RD (28), which may amplify small conformational changes arising in the motor domain by acting as a swinging lever arm (45)(46)(47)(48). Because the mutations studied here do not appreciably change the length of the lever arm, a smaller d could arise from increasing the flexibility of the lever arm region.…”