Identification of binding sites for bepridil and trifluoperazine on cardiac troponin C.

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Kleerekoper Q, Liu W, Choi D, Putkey JA

Identification of binding sites for bepridil and trifluoperazine on cardiac troponin C.

J Biol Chem. 1998 Apr 3;273(14):8153-60.

PubMed ID

9525919 [ View in PubMed

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Abstract

The solution structure of cardiac troponin C (cTnC) (Sia, S., Li, M. X., Spyracopoulos, L., Gagne, S. M., Liu, W., Putkey, J. A. & Sykes, B. D. (1997) J. Biol. Chem. 272, 18216-18221) challenges existing structure/function models for this critical regulatory protein. For example, it is clear that the closed conformation of the regulatory N-terminal domain in Ca2+-bound cardiac troponin C (cTnC) presents a much different binding surface for Ca2+-sensitizing compounds than previously thought. We report here the use of Met methyl groups as site-specific structural markers to identify drug binding sites for trifluoperazine and bepridil on cTnC. Drug dependent changes in the NMR heteronuclear single-quantum coherence spectra of [methyl-13C]Met-labeled cTnC indicate that bepridil and trifluoperazine bind to similar sites but only in the presence of Ca2+. There are 3-4 drug binding sites in the N- and C-terminal domains of intact cTnC that exhibit fast exchange on the NMR time scale. Use of a novel spin-labeled phenothiazine and detection of isotope-filtered nuclear Overhauser effects allowed identification of drug binding sites in the shallow hydrophobic cup in the C-terminal domain and on two hydrophobic surfaces on the N-terminal regulatory domain. The data presented here, coupled with our previous study using covalent blocking groups, support a model in which the Ca2+-sensitizing binding site includes Met-45 in helix B of site I, and Met-60 and -80 in helices B and C of the regulatory site II. This subregion in cTnC makes a likely target against which to design new and selective Ca2+-sensitizing compounds.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Bepridil	Troponin C, slow skeletal and cardiac muscles	Protein	Humans	Unknown	Other	Details
Trifluoperazine	Troponin C, slow skeletal and cardiac muscles	Protein	Humans	Unknown	Not Available	Details