Document Detail

Calcium-dependent movement of troponin I between troponin C and actin as revealed by spin-labeling EPR.
MedLine Citation:
PMID:  16375855     Owner:  NLM     Status:  MEDLINE    
We measured EPR spectra from a spin label on the Cys133 residue of troponin I (TnI) to identify Ca(2+)-induced structural states, based on sensitivity of spin-label mobility to flexibility and tertiary contact of a polypeptide. Spectrum from Tn complexes in the -Ca(2+) state showed that Cys133 was located at a flexible polypeptide segment (rotational correlation time tau=1.9ns) that was free from TnC. Spectra of both Tn complexes alone and those reconstituted into the thin filaments in the +Ca(2+) state showed that Cys133 existed on a stable segment (tau=4.8ns) held by TnC. Spectra of reconstituted thin filaments (-Ca(2+) state) revealed that slow mobility (tau=45ns) was due to tertiary contact of Cys133 with actin, because the same slow mobility was found for TnI-actin and TnI-tropomyosin-actin filaments lacking TnC, T or tropomyosin. We propose that the Cys133 region dissociates from TnC and attaches to the actin surface on the thin filaments, causing muscle relaxation at low Ca(2+) concentrations.
Tomoki Aihara; Shoji Ueki; Motoyoshi Nakamura; Toshiaki Arata
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-12-15
Journal Detail:
Title:  Biochemical and biophysical research communications     Volume:  340     ISSN:  0006-291X     ISO Abbreviation:  Biochem. Biophys. Res. Commun.     Publication Date:  2006 Feb 
Date Detail:
Created Date:  2006-01-03     Completed Date:  2006-03-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0372516     Medline TA:  Biochem Biophys Res Commun     Country:  United States    
Other Details:
Languages:  eng     Pagination:  462-8     Citation Subset:  IM    
Department of Biological Sciences, Graduate School of Science, Osaka University and CREST/JST, Toyonaka, Osaka 560-0043, Japan.
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MeSH Terms
Actins / chemistry,  metabolism*
Calcium / physiology*
Cysteine / metabolism
Electron Spin Resonance Spectroscopy
Protein Structure, Secondary
Spin Labels
Tropomyosin / metabolism
Troponin C / chemistry,  metabolism*
Troponin I / chemistry,  metabolism*
Reg. No./Substance:
0/Actins; 0/Spin Labels; 0/Tropomyosin; 0/Troponin C; 0/Troponin I; 52-90-4/Cysteine; 7440-70-2/Calcium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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