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- Sorsa, T, et al.
(författare)
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Interaction of levosimendan with cadiac troponin C in the presence of cardiac troponin I peptides.
- 2003
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Ingår i: Journal of Molecular and Cellular Cardiology. - 1095-8584. ; 35:9, s. 1055-1061
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between troponin C (TnC) and troponin I (TnI) is essential for the regulation of muscle contraction. There are several binding sites for TnI on TnC that are differentially occupied depending on the phase of the contraction/relaxation cycle. TnI and TnC interact in an antiparallel fashion with each other. The C-domain of cTnC and the N-domain region of cTnI(residues 33–70) always interact under physiological conditions, whereas the interaction between regulatory regions of TnC and TnI (residues 128–166) is calcium dependent. Previously, it has been shown that levosimendan, a calcium sensitizer used as a treatment for acute heart failure, can interact with both domains of isolated cTnC. To understand which interaction is relevant for the mechanism of calcium sensitization, we used a more complete troponin model obtained by complexing cTnI32–79 and cTnI128–180 with calcium-saturated cTnCCS. The cTnI peptides bound to cTnCCS to form a 1:1:1 complex. The interaction of levosimendan with this complex was followed by 1H–15N heteronuclear correlation spectroscopy. It was clear that based on chemical shift changes, cTnI32–79 blocked the levosimendan interaction sites on the C-domain, whereas cTnI128–180 did not compete with levosimendan for the binding site on the N-domain. Hence, the effective binding site of levosimendan on cTnC resulting in the calcium-sensitizing effect is located in the regulatory domain (N-domain).
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- Sorsa, T, et al.
(författare)
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Stereoselective binding of levosimendan to cardiac troponin C causes Ca2+-sensitization
- 2004
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 1879-0712 .- 0014-2999. ; 486:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the Ca2+ sensitizer levosimendan and that of its stereoisomer dextrosimendan on the cardiac contractile apparatus were studied using skinned fibers obtained from guinea pig hearts. Levosimendan was found to be more effective than dextrosimendan in this model. The respective concentrations of levosimendan and dextrosimendan at EC50 were 0.3 and 3 muM. In order to explain the difference in efficacy as Ca2+ sensitizers, the binding of the two stereoisomers on cardiac troponin C was studied by nuclear magnetic resonance in the absence and presence of two peptides of cardiac troponin I. The two stereoisomers interacted with both domains of cardiac troponin C in the absence of cardiac troponin I. In the presence of cardiac troponin I-(32-79) and cardiac troponin I-(128-180), the binding of both levosimendan and dextrosimendan to the C-terminal domain of cardiac troponin C was blocked and only the binding to the N-terminal domain was observable. Differences in the overall binding behavior of the two isomers to cardiac troponin C were highlighted in order to discuss their structure to activity relation. Our data are consistent with the notion that the action of levosimendan as a Ca2+ sensitizer and positive inotrope relates to its stereoselective binding to Ca2+-saturated cardiac troponin C. (C) 2003 Elsevier B.V. All rights reserved.
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