1. Effects of troponin T cardiomyopathy mutations on the calcium sensitivity of the regulated thin filament and the actomyosin cross-bridge kinetics of human β-cardiac myosin.
- Author
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Sommese RF, Nag S, Sutton S, Miller SM, Spudich JA, and Ruppel KM
- Subjects
- Adult, Cardiomyopathies metabolism, Cardiomyopathies pathology, Cardiomyopathy, Dilated genetics, Cardiomyopathy, Dilated metabolism, Cardiomyopathy, Dilated pathology, Cardiomyopathy, Hypertrophic genetics, Cardiomyopathy, Hypertrophic metabolism, Cardiomyopathy, Hypertrophic pathology, Humans, Kinetics, Models, Molecular, Myosin Subfragments metabolism, Protein Structure, Secondary, Tropomyosin metabolism, Troponin T chemistry, Troponin T metabolism, Actin Cytoskeleton metabolism, Actomyosin metabolism, Calcium metabolism, Cardiomyopathies genetics, Mutation, Troponin T genetics, Ventricular Myosins metabolism
- Abstract
Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) lead to significant cardiovascular morbidity and mortality worldwide. Mutations in the genes encoding the sarcomere, the force-generating unit in the cardiomyocyte, cause familial forms of both HCM and DCM. This study examines two HCM-causing (I79N, E163K) and two DCM-causing (R141W, R173W) mutations in the troponin T subunit of the troponin complex using human β-cardiac myosin. Unlike earlier reports using various myosin constructs, we found that none of these mutations affect the maximal sliding velocities or maximal Ca(2+)-activated ADP release rates involving the thin filament human β-cardiac myosin complex. Changes in Ca(2+) sensitivity using the human myosin isoform do, however, mimic changes seen previously with non-human myosin isoforms. Transient kinetic measurements show that these mutations alter the kinetics of Ca(2+) induced conformational changes in the regulatory thin filament proteins. These changes in calcium sensitivity are independent of active, cycling human β-cardiac myosin.
- Published
- 2013
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