Role of the structural domain of troponin C in muscle regulation: NMR studies of Ca2+ binding and subsequent interactions with regions 1-40 and 96-115 of troponin I |
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| Authors: | Mercier P Li M X Sykes B D |
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| Affiliation: | MRC Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. |
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| Abstract: | The interaction between the calcium binding and inhibitory components of troponin is central to the regulation of muscle contraction. In this work, two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (2D-?1H,15N?-HSQC NMR) spectroscopy was used to determine the stoichiometry, affinity, and mechanisms for binding of Ca2+ and two synthetic TnI peptides [TnI1-40 (or Rp40) and TnI96-115] to the isolated C-domain of skeletal troponin C (CTnC). The Ca2+ titration revealed that 2 equiv of Ca2+ binds to sites III and IV of CTnC with strong positive cooperativity and high affinity [dissociation constant (KD)
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