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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
30
pubmed:dateCreated
2008-7-30
pubmed:abstractText
Actin/myosin interactions in vertebrate striated muscles are believed to be regulated by the "steric blocking" mechanism whereby the binding of calcium to the troponin complex allows tropomyosin (TM) to change position on actin, acting as a molecular switch that blocks or allows myosin heads to interact with actin. Movement of TM during activation is initiated by interaction of Ca(2+) with troponin, then completed by further displacement by strong binding cross-bridges. We report x-ray evidence that TM in insect flight muscle (IFM) moves in a manner consistent with the steric blocking mechanism. We find that both isometric contraction, at high [Ca(2+)], and stretch activation, at lower [Ca(2+)], develop similarly high x-ray intensities on the IFM fourth actin layer line because of TM movement, coinciding with x-ray signals of strong-binding cross-bridge attachment to helically favored "actin target zones." Vanadate (Vi), a phosphate analog that inhibits active cross-bridge cycling, abolishes all active force in IFM, allowing high [Ca(2+)] to elicit initial TM movement without cross-bridge attachment or other changes from relaxed structure. However, when stretched in high [Ca(2+)], Vi-"paralyzed" fibers produce force substantially above passive response at pCa approximately 9, concurrent with full conversion from resting to active x-ray pattern, including x-ray signals of cross-bridge strong-binding and TM movement. This argues that myosin heads can be recruited as strong-binding "brakes" by backward-sliding, calcium-activated thin filaments, and are as effective in moving TM as actively force-producing cross-bridges. Such recruitment of myosin as brakes may be the major mechanism resisting extension during lengthening contractions.
pubmed:grant
pubmed:commentsCorrections
http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-10571184, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-10747208, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-10952872, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-114244, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-11719600, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-14169343, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-14765112, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-14990488, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-15111415, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-15298914, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-15310956, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-15662427, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-16574907, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-16793285, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-17085600, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-18077437, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-2100305, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-2338083, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-27795, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-3159090, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-3903036, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-4539699, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-4713300, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-5635532, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-6922391, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-6971661, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-7696481, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-7779179, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-8107884, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-8487194, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-9054965, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-9512040, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-9635278, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-9657517, http://linkedlifedata.com/resource/pubmed/commentcorrection/18658238-9826617
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
1091-6490
pubmed:author
pubmed:issnType
Electronic
pubmed:day
29
pubmed:volume
105
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
10372-7
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
2008
pubmed:articleTitle
Reverse actin sliding triggers strong myosin binding that moves tropomyosin.
pubmed:affiliation
Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL 60616.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S.
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