Load-dependence of the activation of myosin filaments in heart muscle.

ABSTRACT: Contraction of heart muscle requires activation of both the actin and myosin filaments. The mechanism of myosin filament activation is unknown, but the leading candidate hypothesis is direct mechano-sensing by the filaments. Here, we tested this hypothesis by activating intact trabeculae from rat heart by electrical stimulation under different loads and measuring myosin filament activation by X-ray diffraction. Unexpectedly, we found that the distinct structural changes in the myosin filament associated with activation had different dependences on the load. In early activation, all the structural changes indicated faster activation at higher load, as expected from the mechano-sensing hypothesis, but, at later times, the helical order of the myosin motors characteristic of the inactivated s

SUBMITTER: Wang Y 

PROVIDER: S-EPMC11652228 | biostudies-literature | 2024 Dec

REPOSITORIES: biostudies-literature