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[No abstract available]

Direct measurement of the electrogenic activity of purified mitochondrial transhydrogenase has been carried out. To this end, beef‐heart transhydrogenase was isolated and reconstituted with phospholipids to form proteoliposomes. The transhydrogenase proteoliposomes were incorporated into a membrane filter impregnated with a decane solution of phospholipids. It is shown that addition of substrates of either the forward (NADPH and NAD+) or the reverse (NADH and NADP+) transhydrogenase reaction gives rise to an electric potential difference across the proteoliposometreated membrane filter. The electric vector depends upon the direction of the reaction. The proteoliposome‐supplemented compartment charges negatively in the case of the forward reaction and positively in the case of the reverse one. Addition of the reaction products after substrates equalizes the potentials. The transhydrogenase‐treated membrane filter retains the ability to perform transhydrogenase‐linked electrogenesis after removal of excess non‐incorporated proteoliposomes. The electric potential difference reaching 20 mV immediately after the transhydrogenase substrate addition, slowly decreases due to accumulation of the reaction products. Such decay is prevented when the mixture is supplemented with the substrate‐regenerating and product‐utilizing enzymic systems. Under these conditions, a steady continuous electric current of about 10 pA can be observed. Copyright © 1980, Wiley Blackwell. All rights reserved

[No abstract available]

Treatment of Anabaena variabilis membranes with lauryldimethylamine N-oxide yielded two fractions of pigment-protein complexes which were separable by gel filtration on Sepharose 6B. A green fraction was characterized which had a maximum of the chlorophyll long-wave absorption band at 678 nm and a small amount of carotenoid. In this fraction, Photosystem I activity was higher than in another (brownish-green) fraction which had a maximum of the chlorophyll absorption band at 673 nm and which was enriched in carotenoids. Similarly to isolated membranes, proteoliposomes containing pigment-protein complexes took up tetraphenylborate anions and tetraphenylphosphonium cations and were found to be capable of light-dependent membrane potential generation, when associated with a planar phospholipid membrane in the presence of reduced phenazine methosulfate upon illumination. The spatial arrangement of the pigment-protein complexes in the native and artificial membranes is discussed. © 1982.

[No abstract available]

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[No abstract available]

The orientation of Rhodobacter sphaeroides reaction center complexes (RC complexes) in proteoliposomal membranes was investigated by a direct electrometric method. Conditions were found that allow monitoring of only that RC complex fraction that is oriented with its donor side to the inner part of the proteoliposome. It is shown that o-phenanthroline, an inhibitor of electron transfer between primary (QA) and secondary (QB) quinone acceptors, can also inhibit the photoinduced QA reduction. The efficiency of this inhibition depends on the concentration of added ubiquinone. It is assumed that the laser flash-induced o-phenanthroline inhibition of primary dipole (P-870+ · QA-) formation is of a competitive nature. © 1989 Plenum Publishing Corporation.