Journal article
Structural basis for the in situ Ca2+ sensitization of cardiac troponin C by positive feedback from force-generating myosin cross-bridges
Archives of biochemistry and biophysics, Vol.537(2), pp.198-209
09/15/2013
Handle:
https://hdl.handle.net/2376/107043
PMCID: PMC3836555
PMID: 23896515
Abstract
The
in situ
structural coupling between the cardiac troponin (cTn) Ca
2+
-sensitive regulatory switch (CRS) and strong myosin cross-bridges was investigated using Förster resonance energy transfer (FRET). The double cysteine mutant cTnC(T13C/N51C) was fluorescently labeled with the FRET pair 5-(iodoacetamidoethyl)aminonaphthelene-1-sulfonic acid (IAEDENS) and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (DDPM) and then incorporated into detergent skinned left ventricular papillary fiber bundles. Ca
2+
titrations of cTnC(T13C/N51C)
AEDENS/DDPM
-reconstituted fibers showed that the Ca
2+
-dependence of the opening of the N-domain of cTnC (N-cTnC) statistically matched the force–Ca
2+
relationship. N-cTnC opening still occurred steeply during Ca
2+
titrations in the presence of 1 mM vanadate, but the maximal extent of ensemble-averaged N-cTnC opening and the Ca
2+
-sensitivity of the CRS were significantly reduced. At nanomolar, resting Ca
2+
levels, treatment with ADP•Mg in the absence of ATP caused a partial opening of N-cTnC. During subsequent Ca
2+
titrations in the presence of ADP•Mg and absence of ATP, further N-cTnC opening was stimulated as the CRS responded to Ca
2+
with increased Ca
2+
-sensitivity and reduced steepness. These findings supported our hypothesis here that strong cross-bridge interactions with the cardiac thin filament exert a Ca
2+
-sensitizing effect on the CRS by stabilizing the interaction between the exposed hydrophobic patch of N-cTnC and the switch region of cTnI.
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Details
- Title
- Structural basis for the in situ Ca2+ sensitization of cardiac troponin C by positive feedback from force-generating myosin cross-bridges
- Creators
- Daniel C Rieck - Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USAKing-Lun Li - Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USAYexin Ouyang - Department of Integrated Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USAR. John Solaro - Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL 60612, USAWen-Ji Dong - Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
- Publication Details
- Archives of biochemistry and biophysics, Vol.537(2), pp.198-209
- Academic Unit
- Chemical Engineering and Bioengineering, School of
- Grant note
- R01 HL080186 || HL / National Heart, Lung, and Blood Institute : NHLBI
- Identifiers
- 99900546709701842
- Language
- English
- Resource Type
- Journal article