Kinetics of conformational transitions in cardiac troponin induced by Ca2+ dissociation determined by Förster resonance energy transfer

Wen-Ji Dong; John M Robinson; Jun Xing; Herbert C Cheung

doi:10.1074/jbc.M304858200

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Kinetics of conformational transitions in cardiac troponin induced by Ca2+ dissociation determined by Förster resonance energy transfer

Journal article

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Kinetics of conformational transitions in cardiac troponin induced by Ca2+ dissociation determined by Förster resonance energy transfer

Wen-Ji Dong, John M Robinson, Jun Xing and Herbert C Cheung

The Journal of biological chemistry, Vol.278(43), pp.42394-42402

10/24/2003

DOI: https://doi.org/10.1074/jbc.M304858200

Handle:

https://hdl.handle.net/2376/108642

PMID: 12909617

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Abstract

Troponin - metabolism

Spectrometry, Fluorescence - methods

Myocardium - chemistry

Calcium - metabolism

Troponin - genetics

Troponin - chemistry

Rats

Animals

Muscle Contraction

Chickens

Titrimetry

Protein Conformation

Mice

Energy Transfer

Kinetics

Mutation

Protein Subunits - genetics

Upon Ca2+ activation of cardiac muscle, several structural changes occur in the troponin subunits. These changes include the opening of the cardiac troponin C (cTnC) N-domain, the change of secondary structure of the inhibitory region of cardiac troponin I (cTnI), and the change in the separation between these two proteins in the cTnC-cTnI interface. We have used Förster resonance energy transfer in Ca2+ titration and stopped-flow experiments to delineate these transitions using a reconstituted cardiac troponin. Energy transfer results were quantified to yield time-dependent profiles of changes in intersite distances during Ca2+ dissociation. The closing of the cTnC N-domain induced by release of regulatory Ca2+ from cTnC occurs in one step (t1/2 approximately 5 ms), and this transition is not affected by Ca2+ release from the C-domain. The other two transitions triggered by Ca2+ dissociation are biphasic with the fast phase (t1/2 approximately 5 ms) correlated with Ca2+ release from the cTnC N-domain. These transitions are slower than the release of bound regulatory Ca2+ (t1/2 3.6 ms) and are coupled to one another in a cooperative manner in restoring their conformations in the deactivated state. The kinetic results define the magnitudes of structural changes relevant in Ca2+ switching between activation and deactivation of cardiac muscle contraction.

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Title: Kinetics of conformational transitions in cardiac troponin induced by Ca2+ dissociation determined by Förster resonance energy transfer
Creators: Wen-Ji Dong - Department of Biochemistry and Molecular Genetics, University of Alabama, Birmingham, AL 35294-0005, USA. wdong@uab.edu
John M Robinson
Jun Xing
Herbert C Cheung
Publication Details: The Journal of biological chemistry, Vol.278(43), pp.42394-42402
Academic Unit: Chemical Engineering and Bioengineering, School of
Publisher: United States
Grant note: HL 52508 / NHLBI NIH HHS R01 HL080186 / NHLBI NIH HHS
Identifiers: 99900547080901842
Language: English
Resource Type: Journal article