Electrogenesis from an ATPase-ATP-sodium pseudo pump

Abstract

The short circuit current and the open circuit voltage responses of membranes to ATP, which have been attributed to membrane ATPase acting as a sodium pump, have been reproduced not only in a lipid membrane containing solubilized ATPase but also in membranes formed of the phospholipids contained in ATPase. The response is greatest with cardiolipin, but occurs with other acidic phospholipids. This observation of electrogenesis without hydrolysis is a surface phenomenon probably due to the alignment of ATP on the phospholipid by ion association at its interface with the water phase. The finding constitutes a precaution for interpreting studies of membrane Na-K-ATPase or for its incorporation into an artificial membrane. The substances necessary for electrogenesis are present at the mitochondrial membrane, and the particular orientation of the ATP on the phospholipids in vitro suggests a role for this ion association in the function of Na-K-ATPase.

Electrical manifestation of ion transport across black lipid membranes generated by a Na+/K+ ATPase

“…An attempt to reconstitute an electrogenic pump by incorporating a Nd/K' ATPase into BLM resulted in transient electrical responses only with ATP and phospho~pids bound to the ATPase [6]. Here, the problem of the electrogenic pump reconstitution is reconsidered using a Na'/K' ATPase extracted from pork brain, special attention being paid to the incorporation kinetics.…”