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dc.contributor.authorFrado, Ling-Ling Young
dc.contributor.authorCraig, Roger W.
dc.date2022-08-11T08:10:05.000
dc.date.accessioned2022-08-23T16:55:05Z
dc.date.available2022-08-23T16:55:05Z
dc.date.issued1989-08-01
dc.date.submitted2008-10-31
dc.identifier.citationJ Cell Biol. 1989 Aug;109(2):529-38.
dc.identifier.issn0021-9525 (Print)
dc.identifier.pmid2760106
dc.identifier.urihttp://hdl.handle.net/20.500.14038/42639
dc.description.abstractWe have used electron microscopy and proteolytic susceptibility to study the structural basis of myosin-linked regulation in synthetic filaments of scallop striated muscle myosin. Using papain as a probe of the structure of the head-rod junction, we find that this region of myosin is approximately five times more susceptible to proteolytic attack under activating (ATP/high Ca2+) or rigor (no ATP) conditions than under relaxing conditions (ATP/low Ca2+). A similar result was obtained with native myosin filaments in a crude homogenate of scallop muscle. Proteolytic susceptibility under conditions in which ADP or adenosine 5'-(beta, gamma-imidotriphosphate) (AMPPNP) replaced ATP was similar to that in the absence of nucleotide. Synthetic myosin filaments negatively stained under relaxing conditions showed a compact structure, in which the myosin cross-bridges were close to the filament backbone and well ordered, with a clear 14.5-nm axial repeat. Under activating or rigor conditions, the cross-bridges became clumped and disordered and frequently projected further from the filament backbone, as has been found with native filaments; when ADP or AMPPNP replaced ATP, the cross-bridges were also disordered. We conclude (a) that Ca2+ and ATP affect the affinity of the myosin cross-bridges for the filament backbone or for each other; (b) that the changes observed in the myosin filaments reflect a property of the myosin molecules alone, and are unlikely to be an artifact of negative staining; and (c) that the ordered structure occurs only in the relaxed state, requiring both the presence of hydrolyzed ATP on the myosin heads and the absence of Ca2+.
dc.language.isoen_US
dc.relation<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&list_uids=2760106&dopt=Abstract">Link to Article in PubMed</a>
dc.subjectActins
dc.subjectAdenosine Triphosphate
dc.subjectAnimals
dc.subjectCalcium
dc.subjectCytoskeleton
dc.subjectMicrofilaments
dc.subjectMicroscopy, Electron
dc.subjectMolecular Structure
dc.subjectMollusca
dc.subjectMyosins
dc.subjectPapain
dc.subjectCell Biology
dc.titleStructural changes induced in Ca2+-regulated myosin filaments by Ca2+ and ATP
dc.typeJournal Article
dc.source.journaltitleThe Journal of cell biology
dc.source.volume109
dc.source.issue2
dc.identifier.legacyfulltexthttps://escholarship.umassmed.edu/cgi/viewcontent.cgi?article=1968&amp;context=oapubs&amp;unstamped=1
dc.identifier.legacycoverpagehttps://escholarship.umassmed.edu/oapubs/969
dc.identifier.contextkey659151
refterms.dateFOA2022-08-23T16:55:05Z
html.description.abstract<p>We have used electron microscopy and proteolytic susceptibility to study the structural basis of myosin-linked regulation in synthetic filaments of scallop striated muscle myosin. Using papain as a probe of the structure of the head-rod junction, we find that this region of myosin is approximately five times more susceptible to proteolytic attack under activating (ATP/high Ca2+) or rigor (no ATP) conditions than under relaxing conditions (ATP/low Ca2+). A similar result was obtained with native myosin filaments in a crude homogenate of scallop muscle. Proteolytic susceptibility under conditions in which ADP or adenosine 5'-(beta, gamma-imidotriphosphate) (AMPPNP) replaced ATP was similar to that in the absence of nucleotide. Synthetic myosin filaments negatively stained under relaxing conditions showed a compact structure, in which the myosin cross-bridges were close to the filament backbone and well ordered, with a clear 14.5-nm axial repeat. Under activating or rigor conditions, the cross-bridges became clumped and disordered and frequently projected further from the filament backbone, as has been found with native filaments; when ADP or AMPPNP replaced ATP, the cross-bridges were also disordered. We conclude (a) that Ca2+ and ATP affect the affinity of the myosin cross-bridges for the filament backbone or for each other; (b) that the changes observed in the myosin filaments reflect a property of the myosin molecules alone, and are unlikely to be an artifact of negative staining; and (c) that the ordered structure occurs only in the relaxed state, requiring both the presence of hydrolyzed ATP on the myosin heads and the absence of Ca2+.</p>
dc.identifier.submissionpathoapubs/969
dc.contributor.departmentDepartment of Cell Biology
dc.source.pages529-38


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