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The troponin I: inhibitory peptide uncouples force generation and the cooperativity of contractile activation in mammalian skeletal muscle.
MedLine Citation:
PMID:  23340900     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Hodges and his colleagues identified a 12 amino acid fragment of troponin I (TnI-ip) that inhibits Ca(2+)-activated force and reduces the effectiveness Ca(2+) as an activator. To understand the role of troponin C (TnC) in the extended cooperative interactions of thin filament activation, we compared the effect of TnI-ip with that of partial troponin TnC extraction. Both methods reduce maximal Ca(2+)-activated force and increase [Ca(2+)] required for activation. In contrast to TnC extraction, TnI-ip does not reduce the extended cooperative interactions between adjacent thin filament regulatory units as assessed by the slope of the pCa/force relationship. Additional evidence that TnI-ip does not interfere with extended cooperativity comes from studies that activate muscle by rigor crossbridges (RXBs). TnI-ip increases both the cooperativity of activation and the concentration of RXBs needed for maximal force. This shows that TnI-ip binding to TnC increases the stability of the relaxed state of the thin filament. TnI-ip, therefore, uncouples force generation from extended cooperativity in both Ca(2+) and RXB activated muscle contraction. Because maximum force can be reduced with no change-or even an increase-in cooperativity, force-generating crossbridges do not appear to be the primary activators of cooperativity between thin filament regulatory units of skeletal muscle.
Authors:
Fred Schachat; Philip W Brandt
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-23
Journal Detail:
Title:  Journal of muscle research and cell motility     Volume:  -     ISSN:  1573-2657     ISO Abbreviation:  J. Muscle Res. Cell. Motil.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8006298     Medline TA:  J Muscle Res Cell Motil     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Division of Physiology, Department of Cell Biology, Duke University Medical School, Box 3011, Durham, NC, 27710, USA, f.schachat@cellbio.duke.edu.
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