José R Guerrero

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Myosin filaments from many muscles are activated by phosphorylation of their regulatory light chains (RLCs). To elucidate the structural mechanism of activation, we have studied RLC phosphorylation in tarantula thick filaments, whose high-resolution structure is known. In the relaxed state, tarantula RLCs are ~50% non-phosphorylated and 50%(More)
We have applied three-dimensional helical reconstruction techniques to images of myosin filaments of tarantula leg muscle obtained from rapidly frozen, freeze-substituted specimens. Computed Fourier transforms of filaments selected from longitudinal sections show up to six layer lines indexing on the 43.5-nm helical repeat of myosin crossbridges. The(More)
Tarantula leg muscles in the relaxed state were rapidly frozen against a copper block cooled with liquid helium. Thin longitudinal sections of freeze-substituted specimens, both live and skinned, clearly showed the helical tracks of crossbridges on the surface of the myosin filaments, which are not preserved by conventional fixation. Fourier transforms of(More)
Chemically demembranated bundles of fibers from tarantula leg muscle were rapidly frozen in the relaxed state and freeze-substituted in the presence of tannic acid. Electron micrographs of thin transverse sections of freeze-substituted specimens frequently showed four clear, regularly organized projections (crossbridges) protruding from the backbones of the(More)
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