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A troponin switch that regulates muscle contraction by stretch instead of calcium
Author(s) -
Agianian Bogos,
Kržič Uroš,
Qiu Feng,
Linke Wolfgang A,
Leonard Kevin,
Bullard Belinda
Publication year - 2004
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600097
Subject(s) - isometric exercise , myofibril , gene isoform , biology , insect flight , troponin c , myosin , contraction (grammar) , tension (geology) , biophysics , muscle contraction , troponin , calcium , microbiology and biotechnology , anatomy , biochemistry , medicine , endocrinology , compression (physics) , materials science , gene , physics , mechanics , physiology , composite material , myocardial infarction , aerodynamics
The flight muscles of many insects have a form of regulation enabling them to contract at high frequencies. The muscles are activated by periodic stretches at low Ca 2+ levels. The same muscles also give isometric contractions in response to higher Ca 2+ . We show that the two activities are controlled by different isoforms of TnC (F1 and F2) within single myofibrils. F1 binds one Ca 2+ with high affinity in the C‐terminal domain and F2 binds one Ca 2+ in the C‐terminal domain and one exchangeable Ca 2+ in the N‐terminal domain. We have characterised the isoforms and determined their effect on the development of stretch‐activated and Ca 2+ ‐activated tension by replacing endogenous TnC in Lethocerus flight muscle fibres with recombinant isoforms. Fibres with F1 gave stretch‐activated tension and minimal isometric tension; those with F2 gave Ca 2+ ‐dependent isometric tension and minimal stretch‐activated tension. Regulation by a TnC responding to stretch rather than Ca 2+ is unprecedented and has resulted in the ability of insect flight muscle to perform oscillatory work at low Ca 2+ concentrations, a property to which a large number of flying insects owe their evolutionary success.