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 azi- muthal 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.

Structural dynamics of troponin during activation of skeletal muscle / L. Fusi;E. Brunello;I. R. Sevrieva;Y.-B. Sun;M. Irving. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - STAMPA. - 111:(2014), pp. 4626-4631. [10.1073/pnas.1321868111]

Structural dynamics of troponin during activation of skeletal muscle

BRUNELLO, ELISABETTA;
2014

Abstract

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 azi- muthal 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.
2014
111
4626
4631
L. Fusi;E. Brunello;I. R. Sevrieva;Y.-B. Sun;M. Irving
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/847294
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