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Structural changes that occur in scallop myosin filaments upon activation

Myosin filaments isolated from scallop striated muscle have been activated by calcium-containing solutions, and their structure has been examined by electron microscopy after negative staining. The orderly helical arrangement of myosin projections characteristic of the relaxed state is largely lost...

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Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1985
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2113694/
https://www.ncbi.nlm.nih.gov/pubmed/4040918
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description Myosin filaments isolated from scallop striated muscle have been activated by calcium-containing solutions, and their structure has been examined by electron microscopy after negative staining. The orderly helical arrangement of myosin projections characteristic of the relaxed state is largely lost upon activation. The oblique striping that arises from alignment of elongated projections along the long-pitched helical tracks is greatly weakened, although a 145 A axial periodicity is sometimes partially retained. The edges of the filaments become rough, and the myosin heads move outwards as their helical arrangement becomes disordered. Crossbridges at various angles appear to link thick and thin filaments after activation. The transition from order to disorder is reversible and occurs over a narrow range of free calcium concentration near pCa 5.7. Removal of nucleotide, as well as dissociation of regulatory light chains, also disrupts the ordered helical arrangement of projections. We suggest that the relaxed arrangement of the projections is probably maintained by intermolecular interactions between myosin molecules, which depend on the regulatory light chains. Calcium binding changes the interactions between light chains and the rest of the head, activating the myosin molecule. Intermolecular contacts between molecules may thus be altered and may propagate activation cooperatively throughout the thick filament.
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spelling pubmed-21136942008-05-01 Structural changes that occur in scallop myosin filaments upon activation J Cell Biol Articles Myosin filaments isolated from scallop striated muscle have been activated by calcium-containing solutions, and their structure has been examined by electron microscopy after negative staining. The orderly helical arrangement of myosin projections characteristic of the relaxed state is largely lost upon activation. The oblique striping that arises from alignment of elongated projections along the long-pitched helical tracks is greatly weakened, although a 145 A axial periodicity is sometimes partially retained. The edges of the filaments become rough, and the myosin heads move outwards as their helical arrangement becomes disordered. Crossbridges at various angles appear to link thick and thin filaments after activation. The transition from order to disorder is reversible and occurs over a narrow range of free calcium concentration near pCa 5.7. Removal of nucleotide, as well as dissociation of regulatory light chains, also disrupts the ordered helical arrangement of projections. We suggest that the relaxed arrangement of the projections is probably maintained by intermolecular interactions between myosin molecules, which depend on the regulatory light chains. Calcium binding changes the interactions between light chains and the rest of the head, activating the myosin molecule. Intermolecular contacts between molecules may thus be altered and may propagate activation cooperatively throughout the thick filament. The Rockefeller University Press 1985-09-01 /pmc/articles/PMC2113694/ /pubmed/4040918 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Structural changes that occur in scallop myosin filaments upon activation
title Structural changes that occur in scallop myosin filaments upon activation
title_full Structural changes that occur in scallop myosin filaments upon activation
title_fullStr Structural changes that occur in scallop myosin filaments upon activation
title_full_unstemmed Structural changes that occur in scallop myosin filaments upon activation
title_short Structural changes that occur in scallop myosin filaments upon activation
title_sort structural changes that occur in scallop myosin filaments upon activation
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2113694/
https://www.ncbi.nlm.nih.gov/pubmed/4040918