Reconstitution of biological molecular generators of electric current. Inorganic pyrophosphatase

Abstract

Proteoliposomes have been reconstituted from soy-bean phospholipids (asolectin) and inorganic pyrophosphatase isolated from Rhodospirillum rubrum chromatophores. In the presence of Mg2+ ions, pyrophosphatase proteoliposomes were incorporated into a phospholipid-impregnated Teflon filter separating two solutions of an identical electrolyte content. Addition of inorganic pyrophosphate to the same compartment as proteoliposomes was found to induce generation of an electric potential difference between the two filter-separated compartments, the proteoliposomes-containing compartment being negatively charged. An electric potential difference of 15 mV and a current of 20 pA were observed. The electrogenic effect required Mg2+ and proved to be sensitive to fluoride, an inorganic pyrophosphatase inhibitor. Treatment with 10 microM N,N'-dicyclohexylcarbodiimide for several minutes was without influence upon pyrophosphate-induced membrane potential generation. Similar results were obtained in experiments with a proteoliposome suspension and a penetrating anion, tetraphenyl borate, which is a probe for membrane potential. The obtained data are discussed in connection with the results of studies on other enzymes as molecular generators of electric current.