Arsenate-induced fluorescence changes in the Ca(2+)-ATPase of sarcoplasmic reticulum membranes.
Arsenate, an analogue of inorganic phosphate, causes an increase in the intrinsic fluorescence of the Ca(2+)-ATPase of sarcoplasmic reticulum membranes. This increase in fluorescence is observed regardless of whether Ca(2+)-loaded or leaky vesicles are assayed. The maximal fluorescence change (2-3%) is observed at pH 6.0 in the presence of Mg2+ and is abolished by the addition of micromolar Ca2+ concentrations. Dimethyl sulfoxide (20% v/v) increases the enzyme's affinity for arsenate one order of magnitude. It is concluded that arsenate, after binding, promotes the same conformational change of the enzyme as that produced by Pi.
Alves
E W
EW
Departamento de Bioquimica, Universidade Federal do Rio de Janeiro, Brazil.
D000818:Animals; D001149:Arsenates / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D010710:Phosphates / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D001149:Arsenates; D010710:Phosphates; C025657:arsenic acid; D002118:Calcium