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Voltage‐dependent pump currents of the sarcoplasmic reticulum Ca 2+ ‐ATPase in planar lipid membranes
Author(s) -
Eisenrauch Andreas,
Bamberg Ernst
Publication year - 1990
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(90)80996-v
Subject(s) - endoplasmic reticulum , atp hydrolysis , chemistry , biophysics , atpase , membrane , vesicle , membrane potential , intracellular , ion pump , ion , enzyme , biochemistry , biology , organic chemistry
Sarcoplasmic reticulum vesicles containing largely Ca 2+ ‐ATPase were incorporated into planar lipid membranes. The ATPase was activated by a UV flash‐induced concentration jump of ATP from a photolabile caged ATP. Under these conditions stationary pump currents were observed. The dependence of these pump currents on applied voltages was investigated. The current‐voltage curve of the Ca 2+ ‐ATPase shows monotonously increasing pump currents with increasing positive potentials of the ATP containing compartment. This indicates the existence of electrogenic steps in the direction of the transported Ca 2+ ions. From the extrapolated reversal potentials of the curve is concluded that less than four positive net charges are transported per hydrolyzed ATP.