A new structural state of myosin.

The mechanism by which motor proteins hydrolyze ATP and move along cytoskeletal filaments is still unknown. One approach to deciphering the mechanism is to correlate steps of ATP hydrolysis with structural states of the motors to determine the changes the motors undergo during the hydrolysis cycle. Unfortunately, available crystal structures represent only a few steps of the cycle and obtaining atomic structures that represent the motors bound to their filament has been difficult. Now, two new myosin crystal structures have been reported that show features expected for myosin motors bound in rigor to actin. The two new structures show changes at both the actin-binding surface and the active site that have not been observed previously.