Evidence for the Essential Role of Myosin Subfragment-2 in the ATP-Dependent Actin-Myosin Sliding in Muscle Contraction
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The role of myosin subfragment-2 (myosin S-2) in muscle contraction was studied by using an in vitro motility assay system in which the ATP-dependent sliding between myosin-coated polystyrene beads and actin filament arrays (actin cables) of giant algal cells were recorded under constant external loads provided with a centrifuge microscope. With antibody to myosin S-2 below 0.3 mg/ml, the maximum “isometric” force generated by myosin molecules on the bead decreased markedly, but the unloaded bead-sliding velocity along actin cables did not change appreciably, indicating a decrease in the number of myosin molecules interacting with actin scables. The antibody at 0.3-1.5 mg/ml decreased not only the maximum isometric force, but also the unloaded bead-sliding velocity in a dose-dependent manner. With the antibody at 1.5-3 mg/ml, the beads eventually stopped moving to remain attached to actin cables. These beads could be readily detached from actin cables with very small centrifugal forces, indicating very weak actin-myosin linkages. The antibody had no effect on rigor actin myosin linkages fromed before the antibody application. These results are consistent with the view that myosin S-2 plays an essential role in muscle contraction.
- The Japanese Journal of Physiology
The Japanese Journal of Physiology 48(5), 383-387, 1998-10
THE PHYSIOLOGICAL SOCIETY OF JAPAN