Robertson Ian M, Pineda-Sanabria Sandra E, Yan Ziqian, Kampourakis Thomas, Sun Yin-Biao, Sykes Brian D, Irving Malcolm
Randall Division of Cell and Molecular Biophysics and British Heart Foundation Centre of Research Excellence, King's College London , New Hunt's House, Guy's Campus, London, SE1 1UL, U.K.
Department of Biochemistry, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta T6G 2H7, Canada.
Biochemistry. 2016 Nov 1;55(43):6032-6045. doi: 10.1021/acs.biochem.6b00758. Epub 2016 Oct 17.
The binding of Ca to cardiac troponin C (cTnC) triggers contraction in heart muscle. In the diseased heart, the myocardium is often desensitized to Ca, which leads to impaired contractility. Therefore, compounds that sensitize cardiac muscle to Ca (Ca-sensitizers) have therapeutic promise. The only Ca-sensitizer used regularly in clinical settings is levosimendan. While the primary target of levosimendan is thought to be cTnC, the molecular details of this interaction are not well understood. In this study, we used mass spectrometry, computational chemistry, and nuclear magnetic resonance spectroscopy to demonstrate that levosimendan reacts specifically with cysteine 84 of cTnC to form a reversible thioimidate bond. We also showed that levosimendan only reacts with the active, Ca-bound conformation of cTnC. Finally, we propose a structural model of levosimendan bound to cTnC, which suggests that the Ca-sensitizing function of levosimendan is due to stabilization of the Ca-bound conformation of cTnC.
钙离子与心肌肌钙蛋白C（cTnC）的结合会触发心肌收缩。在患病心脏中，心肌通常会对钙离子脱敏，这会导致收缩力受损。因此，使心肌对钙离子敏感的化合物（钙离子增敏剂）具有治疗前景。临床中经常使用的唯一一种钙离子增敏剂是左西孟旦。虽然左西孟旦的主要靶点被认为是cTnC，但这种相互作用的分子细节尚未得到很好的理解。在本研究中，我们使用质谱、计算化学和核磁共振光谱来证明左西孟旦与cTnC的半胱氨酸84特异性反应，形成可逆的硫代亚胺键。我们还表明，左西孟旦仅与cTnC的活性、钙离子结合构象反应。最后，我们提出了左西孟旦与cTnC结合的结构模型，这表明左西孟旦的钙离子增敏功能是由于cTnC的钙离子结合构象的稳定。
