Time-resolved X-ray diffraction studies of the structural behaviour of myosin heads in a living contracting unstriated muscle.
The intensities of three regions of the low-angle X-ray diffraction pattern from a molluscan unstriated muscle have been followed during tension generation at a time resolution of 0.5-1 s using synchrotron radiation. The observed intensity changes can be reasonably interpreted in terms of myosin cross-bridge movements during the contractile cycle. A model that accounts for the intensity changes suggests that myosin heads move out from the thick filament during activation and attach to actin sites to produce tension with a small delay. During relaxation from both phasic and tonic contractions the heads remain attached to actin sites longer than it takes for tension to decay.
D000199:Actins; D049872:Bivalvia; D008954:Models, Biological; D009119:Muscle Contraction; D009218:Myosins; D011487:Protein Conformation; D014961:X-Ray Diffraction
D000199:Actins; D009218:Myosins