Evidence for direct involvement of the sarcoplasmic reticulum Ca(2+)-ATPase in a passive monovalent cation (K+/Na+) exchange

• Published in: FEBS letters Vol. 376; no. 3; pp. 167 - 171
• Main Authors: de Jesus, F, Cuillel, M, Dupont, Y
• Format: Journal Article
• Language: English
• Published: England 04-12-1995
• Subjects: Animals; Biological Transport, Active; Calcium - metabolism; Calcium-Transporting ATPases - antagonists & inhibitors; Calcium-Transporting ATPases - metabolism; Cell-Free System; Enzyme Inhibitors - pharmacology; Gramicidin - pharmacology; Hydrogen-Ion Concentration; Ionophores - pharmacology; Membrane Potentials; Potassium - metabolism; Rabbits; Sarcoplasmic Reticulum - enzymology; Sodium - metabolism; Terpenes - pharmacology; Thapsigargin; Valinomycin - pharmacology
• ISSN: 0014-5793
• DOI: 10.1016/0014-5793(95)01267-1

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.