Journal article
Structural Dynamics of C-domain of Cardiac Troponin I Protein in Reconstituted Thin Filament
The Journal of biological chemistry, Vol.287(10), pp.7661-7674
03/02/2012
Handle:
https://hdl.handle.net/2376/107110
PMCID: PMC3293551
PMID: 22207765
Abstract
Background:
The kinetics and dynamics of the C-domain of cTnI were studied.
Results:
Fluorescence anisotropy data show support for the fly casting model and a fourth state of thin filament activation.
Conclusion:
The fly casting model holds true in the thin filament, but the presence of S1 modulates the process.
Significance:
Our study provides information on the role of the cTnI C-domain in thin filament regulation.
The regulatory function of cardiac troponin I (cTnI) involves three important contiguous regions within its C-domain: the inhibitory region (IR), the regulatory region (RR), and the mobile domain (MD). Within these regions, the dynamics of regional structure and kinetics of transitions in dynamic state are believed to facilitate regulatory signaling. This study was designed to use fluorescence anisotropy techniques to acquire steady-state and kinetic information on the dynamic state of the C-domain of cTnI in the reconstituted thin filament. A series of single cysteine cTnI mutants was generated, labeled with the fluorophore tetramethylrhodamine, and subjected to various anisotropy experiments at the thin filament level. The structure of the IR was found to be less dynamic than that of the RR and the MD, and Ca
2+
binding induced minimal changes in IR dynamics: the flexibility of the RR decreased, whereas the MD became more flexible. Anisotropy stopped-flow experiments showed that the kinetics describing the transition of the MD and RR from the Ca
2+
-bound to the Ca
2+
-free dynamic states were significantly faster (53.2–116.8 s
−1
) than that of the IR (14.1 s
−1
). Our results support the fly casting mechanism, implying that an unstructured MD with rapid dynamics and kinetics plays a critical role to initiate relaxation upon Ca
2+
dissociation by rapidly interacting with actin to promote the dissociation of the RR from the N-domain of cTnC. In contrast, the IR responds to Ca
2+
signals with slow structural dynamics and transition kinetics. The collective findings suggested a fourth state of activation.
Metrics
11 Record Views
Details
- Title
- Structural Dynamics of C-domain of Cardiac Troponin I Protein in Reconstituted Thin Filament
- Creators
- Zhiqun Zhou - From theKing-Lun Li - Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164Daniel Rieck - Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164Yexin Ouyang - From theMurali Chandra - Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164Wen-Ji Dong - From the
- Publication Details
- The Journal of biological chemistry, Vol.287(10), pp.7661-7674
- Academic Unit
- Integrative Physiology and Neuroscience, Department of; Chemical Engineering and Bioengineering, School of
- Publisher
- American Society for Biochemistry and Molecular Biology; 9650 Rockville Pike, Bethesda, MD 20814, U.S.A
- Grant note
- HL80186; HL80186-5S1; HL075643 / National Institutes of Health
- Identifiers
- 99900546533101842
- Language
- English
- Resource Type
- Journal article