Ca2+-induced conformational changes in cardiac troponin C as measured by N-(1-pyrene)maleimide fluorescence.
Bovine cardiac troponin C was modified by N-(1-pyrene)maleimide at Cys-35 and Cys-84; the Ca2+-induced conformational changes were followed by measuring pyrene fluorescence. In isolated troponin C, the saturation of Ca2+, Mg2+-sites leads to a simultaneous increase in the pyrene monomer as well as to a decrease in the pyrene excimer fluorescence, whereas the saturation of Ca2+-specific sites results in a slight decrease in the fluorescence of pyrene monomer. Troponin T does not influence the dependence of pyrene-troponin C fluorescence on Ca2+ concentration. Within the equimolar complex of troponin C and troponin I, the saturation of Ca2+, Mg2+-sites has no effect on pyrene fluorescence, whereas the saturation of Ca2+-specific sites leads to a simultaneous decrease of both pyrene monomer and pyrene excimer fluorescence. It is supposed that troponin I diminishes the conformational changes in troponin C that are induced by the saturation of Ca2+, Mg2+-sites and enhances the conformational changes induced by the saturation of Ca2+-specific sites of troponin C.
Verin
A D
AD
Department of Biochemistry, School of Biology, Moscow State University, U.S.S.R.
Gusev
N B
NB
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000378:metabolism; D008301:Maleimides; D009206:Myocardium / Q000201:enzymology*; D011487:Protein Conformation; D014336:Troponin / Q000378:metabolism*; D019209:Troponin C
D002413:Cations, Divalent; D008301:Maleimides; D014336:Troponin; D019209:Troponin C; C003944:N-(3-pyrene)maleimide; D008274:Magnesium; D002118:Calcium