Structure of cardiac muscle troponin C unexpectedly reveals a closed regulatory domain.Sia, S.K., Li, M.X., Spyracopoulos, L., Gagne, S.M., Liu, W., Putkey, J.A., Sykes, B.D.
(1997) J.Biol.Chem. 272: 18216-18221
- PubMed: 9218458
- DOI: 10.1074/jbc.272.29.18216
- Primary Citation of Related Structures:
- PubMed Abstract:
The regulation of cardiac muscle contraction must differ from that of skeletal muscles to effect different physiological and contractile properties. Cardiac troponin C (TnC), the key regulator of cardiac muscle contraction, possesses different functi ...
The regulation of cardiac muscle contraction must differ from that of skeletal muscles to effect different physiological and contractile properties. Cardiac troponin C (TnC), the key regulator of cardiac muscle contraction, possesses different functional and Ca2+-binding properties compared with skeletal TnC and features a Ca2+-binding site I, which is naturally inactive. The structure of cardiac TnC in the Ca2+-saturated state has been determined by nuclear magnetic resonance spectroscopy. The regulatory domain exists in a "closed" conformation even in the Ca2+-bound (the "on") state, in contrast to all predicted models and differing significantly from the calcium-induced structure observed in skeletal TnC. This structure in the Ca2+-bound state, and its subsequent interaction with troponin I (TnI), are crucial in determining the specific regulatory mechanism for cardiac muscle contraction. Further, it will allow for an understanding of the action of calcium-sensitizing drugs, which bind to cardiac TnC and are known to enhance the ability of cardiac TnC to activate cardiac muscle contraction.
Department of Biochemistry, Medical Research Council Group in Protein Structure and Function, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.