Reconstitution of biological molecular generators of electric current. H+-ATPase

1. Generation of a transmembrane electric potential difference by oligomycin-sensitive ATPase complex, incorporated into spherical or planar phospholipid membrane, has been demonstrated. To this end, penetrating anion probe and direct voltmeter measurement of electric potential across phospholipid membrane were used. It was found that ATP-induced electric response is sensitive to oligomycin and protonophorous uncouplers. 2. The effect of variations in the phospholipid component of proteoliposomes on the electric generation was studied. It was revealed that the usage of mitochondrial phospholipids and phosphatidylethanolamine allows the highest values of membrane potential to be obtained in the case of ATPase proteoliposomes. In the case of cytochrome oxidase and bacteriorhodopsin proteoliposomes, phosphatidylserine was also shown to be quite suitable. Phosphatidylcholine was absolutely ineffective in all cases. 3. In proteoliposomes, containing both ATPase and bacteriorhodopsin, ATP and light induced generation of the electric field of the same direction. 4. In ATPase + cytochrome oxidase proteoliposomes, ATP hydrolysis and ascorbate oxidation was found to support electric generation of the same direction if cytochrome c was inside vesicles. Oxidation via external cytochrome c resulted in formation of electric field of the direction, opposite to that induced by ATP hydrolysis. 5. The data obtained in experiments with proteoliposomes of different types are discussed. The conclusion is made that conversion of energy of different resources into electric form is a common feature of membraneous energy transducers, which is in agreement with the Mitchellian principle of cellular energetics.