Voltage-dependent pump currents of the sarcoplasmic reticulum Ca2(+)-ATPase in planar lipid membranes |
| |
Authors: | A Eisenrauch E Bamberg |
| |
Affiliation: | Max-Planck-Institut für Biophysik, Frankfurt am Main, FRG. |
| |
Abstract: | Sarcoplasmic reticulum vesicles containing largely Ca2(+)-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 Ca2(+)-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 Ca2+ ions. From the extrapolated reversal potentials of the curve is concluded that less than four positive net charges are transported per hydrolyzed ATP. |
| |
Keywords: | |
|
|