Structural dynamics of troponin during activation of skeletal muscle

• DOI: 10.1073/pnas.1321868111
• Publication Date: 2014-03-11T01:34:20Z
• Authors: Luca Fusi; Elisabetta Brunello; Ivanka R. Sevrieva; Yin-Biao Sun; Malcolm Irving
• Keywords: 0301 basic medicine; 570; muscle regulation; Excitation-contraction coupling; muscle signalling; Protein Conformation; 500; 03 medical and health sciences; Animals; Calcium; Rabbits; Muscle, Skeletal; Troponin C; Fluorescent Dyes; Protein Binding

Significance Muscle contraction is controlled by structural changes in the thin filament of the muscle sarcomere triggered by calcium binding to troponin. It has long been suspected that myosin binding has an additional effect in switching on the thin filament, but the biological function of this effect was unknown. We have elucidated the in situ sequence of calcium-induced structural changes of troponin and identified a kinetic component tracking myosin binding to the thin filament. We propose a model of muscle regulation with kinetics determined by coordinated changes in the structures of both thick and thin filaments in response to mechanical conditions rather than, as in the conventional view, solely by the calcium transient and structural changes in the thin filament.