Premium
The mobility of troponin C and troponin I in muscle
Author(s) -
Li HuiChun,
Hideg Kalman,
Fajer Piotr G.
Publication year - 1997
Publication title -
journal of molecular recognition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.401
H-Index - 79
eISSN - 1099-1352
pISSN - 0952-3499
DOI - 10.1002/(sici)1099-1352(199707/08)10:4<194::aid-jmr365>3.0.co;2-x
Subject(s) - microsecond , biophysics , chemistry , electron paramagnetic resonance , nanosecond , spin label , actin , troponin c , myosin , gelsolin , skeletal muscle , troponin , biochemistry , nuclear magnetic resonance , anatomy , biology , medicine , membrane , laser , physics , astronomy , myocardial infarction , optics
In vertebrate skeletal muscle, contraction is initiated by the elevation of the intracellular Ca 2+ concentration. The binding of Ca 2+ to TnC induces a series of conformational changes which ultimately release the inhibition of the actomyosin ATPase activity by Tnl. In this study we have characterized the dynamic behavior of TnC and Tnl in solution, as well as in reconstituted fibers, using EPR and ST‐EPR spectroscopy. Cys98 of TnC and Cys133 of Tnl were specifically labeled with malemide spin label (MSL) and indane dione nitroxide spin label (InVSL). In solution, the labeled TnC and Tnl exhibited fast nanosecond motion. MSL‐TnC is sensitive to cation binding to the high affinity sites (τ r increases from 1.5 to 3.7 ns), InVSL‐TnC s sensitive to the replacement of Mg 2+ by Ca 2+ at these sites (τ r increase from 1.7 to 6 ns). Upon reconstitution into fibers, the nanosecond mobility is reduced by interactions with other proteins. TnC and Tnl both exhibited microsecond anisotropic motion in fibers similar to that of the actin monomers within the filament. The microsecond motion of TnC was found to be modulated by the binding of Ca 2+ and by cross‐bridge attachment, but this was not the case for the global mobility of Tnl. © 1997 John Wiley & Sons, Ltd.