Progress in imaging techniques and nano-manipulation of single molecules ha
s been remarkable. These techniques have allowed the accurate determination
of myosin-head-induced displacements and of how the mechanical cycles of t
he actomyosin motor are coupled to ATP hydrolysis. This has been achieved b
y measuring mechanical and chemical events of actomyosin directly at the si
ngle molecule level. Recent studies have made detailed measurements of myos
in step size and mechanochemical coupling. The results of these studies sug
gest a new model for the mechanism of motion underlying actomyosin motors,
which differs from the currently accepted lever-arm swinging model.