Effects of troponin I phosphorylation on conformational exchange in the regulatory domain of cardiac troponin C. |
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| Authors: | V Gaponenko E Abusamhadneh M B Abbott N Finley G Gasmi-Seabrook R J Solaro M Rance P R Rosevear |
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| Institution: | Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267, USA. |
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| Abstract: | Conformational exchange has been demonstrated within the regulatory domain of calcium-saturated cardiac troponin C when bound to the NH2-terminal domain of cardiac troponin I-(1-80), and cardiac troponin I-(1-80)DD, having serine residues 23 and 24 mutated to aspartate to mimic the phosphorylated form of the protein. Binding of cardiac troponin I-(1-80) decreases conformational exchange for residues 29, 32, and 34. Comparison of average transverse cross correlation rates show that both the NH2- and COOH-terminal domains of cardiac troponin C tumble with similar correlation times when bound to cardiac troponin I-(1-80). In contrast, the NH2- and COOH-terminal domains in free cardiac troponin C and cardiac troponin C bound cardiac troponin I-(1-80)DD tumble independently. These results suggest that the nonphosphorylated cardiac specific NH2 terminus of cardiac troponin I interacts with the NH2-terminal domain of cardiac troponin C. |
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