Myosin is an ATP-driven motor that works on actin filaments. Its head binds actin, releases phosphate and swings a lever arm. This swing is the power stroke. ATP binding then frees the head, and hydrolysis re-cocks the lever for the next cycle. Myosin classes share the head but differ in lever length, direction and time spent bound to actin.
about 11 nm
Stroke per head, muscle myosin
25Mean step of a single myosin molecule at low load in a laser trap. A later single-head study found about 4 nm (Molloy et al. 1995), so the stroke size is disputed.
3-4 pN
Mean isometric force transient of a single myosin molecule.
93 degrees
Myosin-5, primed to post-power stroke, by time-resolved cryo-EM. The swing runs mostly along the actin axis.
about 37 nm
Centre-of-mass step per ATP, hand-over-hand. It matches the 36 nm pseudo-repeat of actin.
about 0.7
Fraction of the cycle a single head spends strongly bound to actin. Muscle myosin spends a small fraction bound and works in large ensembles.
10.4 nm
Lever length, scallop head
Converter (Cα 707) to the end of the heavy-chain helix (Cα 835). Measured by this site from PDB 1QVI.
linear
Velocity versus lever length
19Dictyostelium myosins glide at a speed proportional to neck length. Shorter necks glide slower and a longer neck glides faster.
2.75 nm, -166.7°
Rise and twist per subunit in the Mg-ADP filament (PDB 8A2T). The two long-pitch strands cross about every 37.2 nm.