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Does intrinsic fluorescence reflect conformational changes in the Ca 2+ ‐ATPase of sarcoplasmic reticulum?
Author(s) -
Champeil Philippe,
Le Maire Marc,
Moller Jesper V.,
Riollet Sylvie,
Guillain Florent,
Green N.Michael
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)81347-3
Subject(s) - chemistry , endoplasmic reticulum , fluorescence , biophysics , dephosphorylation , atpase , calcium atpase , kinetics , quenching (fluorescence) , calcium , tryptophan , conformational change , fluorescence anisotropy , phosphorylation , biochemistry , membrane , phosphatase , enzyme , biology , amino acid , physics , organic chemistry , quantum mechanics
We have investigated the kinetics of the intrinsic fluorescence drop observed when ATP is added to purified sarcoplasmic reticulum ATPase in a potassium‐free medium containing magnesium and calcium, at pH 6 and 20°C. Under these conditions, analysis of the fluorescence drop is complex. Several events contributed to the rate of the fluorescence drop initiated by turnover, including phosphorylation, conformational transition of the phosphorylated complex, and dephosphorylation. On the other hand, when 75% of total fluorescence was quenched by energy transfer to the membrane‐bound ionophore A23187, the observed turnoverdependent drop in residual fluorescence mainly reflected the conformational transition of the phosphorylated ATPase. Combination of fast kinetics with the quenching of selected tryptophan residues is suggested to be a promising tool for the study of proteins containing many of these residues.