Effects of troponin I phosphorylation on conformational exchange in the regulatory domain of cardiac troponin C.
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.
Gaponenko
V
V
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267, USA.
Abusamhadneh
E
E
Abbott
M B
MB
Finley
N
N
Gasmi-Seabrook
G
G
Solaro
R J
RJ
Rance
M
M
Rosevear
P R
PR
D001224:Aspartic Acid / Q000235:genetics; D003198:Computer Simulation; D009154:Mutation; D009206:Myocardium; D019906:Nuclear Magnetic Resonance, Biomolecular; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D012694:Serine / Q000235:genetics; D012996:Solutions; D019209:Troponin C / Q000737:chemistry / Q000378:metabolism*; D019210:Troponin I / Q000378:metabolism*
D012996:Solutions; D019209:Troponin C; D019210:Troponin I; D001224:Aspartic Acid; D012694:Serine