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Evidence for direct involvement of the sarcoplasmic reticulum Ca(2+)-ATPase in a passive monovalent cation (K+/Na+)
F de Jesus1, M Cuillel, Y Dupont
1C.E.A., URA CNRS no. 520, Département de Biologie Moléculaire et Structurale, Centre d'Etudes Nucléaires de Grenoble, France.
FEBS Letters
|December 4, 1995
Abstract:
A specific inhibitor of SERCA-pumps, thapsigargin (TG) was used to demonstrate the direct involvement of the SR Ca(2+)-ATPase in passive K+/Na+ exchange. The K(+)-potential variations across vesicle membranes were measured in the absence of ATP with a fluorescent probe: 3,3'-dipropylthiodicarbocyanine iodide. Addition of EGTA dissipates the K(+)-potential whereas the presence of TG abolishes this effect. Our data prove that the Ca(2+)-ATPase translocates monovalent cations at a rate similar to the E2-->E1 conformational change.