Ca2+-induced conformational changes in cardiac troponin C as measured by N-(1-pyrene)maleimide fluorescence

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Abstract

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.

Original languageEnglish (US)
Pages (from-to)197-208
Number of pages12
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume956
Issue number2
DOIs
StatePublished - Sep 21 1988
Externally publishedYes

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Keywords

  • (Bovine heart)
  • Cation induced conformational change
  • N-(1-pyrene)maleimide fluorescence
  • Troponin C

ASJC Scopus subject areas

  • Structural Biology
  • Biophysics
  • Biochemistry
  • Molecular Biology

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