期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 111, 期 12, 页码 4626-4631出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1321868111
关键词
muscle regulation; excitation-contraction coupling; muscle signaling
资金
- Medical Research Council
- Wellcome Trust, United Kingdom
- Fondo per gli Investimenti della Ricerca di Base-Futuro in Ricerca [RBFR08JAMZ]
- British Heart Foundation (BHF)
- British Heart Foundation [FS/09/001/26329] Funding Source: researchfish
- Medical Research Council [G0601065] Funding Source: researchfish
- MRC [G0601065] Funding Source: UKRI
Time-resolved changes in the conformation of troponin in the thin filaments of skeletal muscle were followed during activation in situ by photolysis of caged calcium using bifunctional fluorescent probes in the regulatory and the coiled-coil (IT arm) domains of troponin. Three sequential steps in the activation mechanism were identified. The fastest step (1,100 s(-1)) matches the rate of Ca2+ binding to the regulatory domain but also dominates the motion of the IT arm. The second step (120 s(-1)) coincides with the azimuthal motion of tropomyosin around the thin filament. The third step (15 s(-1)) was shown by three independent approaches to track myosin head binding to the thin filament, but is absent in the regulatory head. The results lead to a four-state structural kinetic model that describes the molecular mechanism of muscle activation in the thin filament-myosin head complex under physiological conditions.
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