Muscle activation in scallop fibers caused a substantial change in myosin head orientations, indicating that 17% ± 2% undergo a large axial rotation upon force generation.
Demonstrates a distinct axial rotation of the myosin light chain domain during muscle contraction using electron paramagnetic resonance, providing insight into motor protein structural transitions.
For more than 30 years, the fundamental goal in molecular motility has been to resolve force-generating motor protein structural changes. Although low-resolution structural studies have provided evidence for force-generating myosin rotations upon muscle activation, these studies did not resolve structural states of myosin in contracting muscle. Using electron paramagnetic resonance, we observed two distinct orientations of a spin label attached specifically to a single site on the light chain domain of myosin in relaxed scallop muscle fibers. The two probe orientations, separated by a 36 degrees +/- 5 degrees axial rotation, did not change upon muscle activation, but the distribution between them changed substantially, indicating that a fraction (17% +/- 2%) of myosin heads undergoes a large (at least 30 degrees) axial rotation of the myosin light chain domain upon force generation and muscle contraction. The resulting model helps explain why this observation has remained so elusive and provides insight into the mechanisms by which motor protein structural transitions drive molecular motility.
Baker et al. (Tue,) conducted a other in Muscle contraction. Muscle activation vs. Relaxed state was evaluated on Axial rotation of the myosin light chain domain. Muscle activation in scallop fibers caused a substantial change in myosin head orientations, indicating that 17% ± 2% undergo a large axial rotation upon force generation.
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