How do molecular motors work?
The myosin motility cycle Myosin binds ATP, hydrolyses the b-g phosphate bond, releases phosphate, and then releases ADP. ATP can rebind to restart the cycle. These chemical transitions produce conformational changes as seen in the movie. • ATP binding causes myosin to release from actin. • ATP hydrolysis is thought to “recock” the myosin lever arm. • Actin binding helps to dissociate phosphate. • Phosphate release causes myosin to bind very tightly to actin and then causes the rotation of a lever arm domain (~10 nm displacement- the “power stroke”). • ADP release is needed to reset the cycle (not shown in the movie but this step might be sensitive to tension- more tension slows down release of ADP so that you can produce force for a longer time). Many myosins simultaneously producing 10 nm strokes cause sarcomeres to shorten and your muscle to contract. Muscle myosin is not processive- it takes a “stroke” and then detaches from actin for most of its ATPase cycle. This is good for cont
