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Incorporation of Beef Heart Cytochrome c Oxidase as a Proton-Motive Force-Generating Mechanism in Bacterial Membrane Vesicles
Arnold J. M. Driessen, Wim De Vrij and Wil N. Konings
Proceedings of the National Academy of Sciences of the United States of America
Vol. 82, No. 22 (Nov. 15, 1985), pp. 7555-7559
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/26413
Page Count: 5
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Membrane vesicles derived from the strictly fermentative lactic acid bacterium Streptococcus cremoris have been fused with proteoliposomes containing the beef heart mitochondrial cytochrome c oxidase by means of a freeze/thawsonication technique. Evidence that fusion has taken place was obtained by freeze-etch electron microscopy, showing a lessdense intramembranous particle distribution in the fused membranes that in the bacterial membranes, and by sucrose gradient centrifugation, indicating a buoyant density of the majority of the membranes after fusion that was between the buoyant densities of the starting membrane preparations. In the fused membranes, 55-60% of the cytochrome c oxidase molecules are oriented with the cytochrome c binding site at the outer surface of the membrane. With the electron-donor system ascorbate/N,N,N′,N′-tetramethyl-p-phenylenediamine/cytochrome c, a high proton-motive force (>130 mV), inside negative and alkaline, can be generated in the fused membrane, and this proton-motive force can drive secondary transport of several amino acids. The procedure described can be used for incorporating a proton-motive force-generating system in isolated membrane vesicles from bacterial or eukaryotic origin that lack a suitable primary proton pump.
Proceedings of the National Academy of Sciences of the United States of America © 1985 National Academy of Sciences