Reconstitution of electrogenic function of pyrophosphatase isolated from Rhodospirillum rubrum membranes

[No abstract available

Reconstitution of electrogenic function in isolated pigment-protein complexes of Anabaena variabilis

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

Reconstitution of Biological Molecular Generators of Electric Current Inorganic Pyrophosphatase

Proteoliposomes have been reconstituted from soy‐bean phospholipids (asolectin) and inorganic pyrophosphatase isolated from Rhodospirillum rubrum chromatophores. In the presence of Mg2+ ions, pyrophosphatase proteolinosomes 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 μM 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. Copyright © 1980, Wiley Blackwell. All rights reserve