Abstract
Membrane vesicles isolated from Azotobacter vinelandii strain O by lysis of spheroplasts in potassium of sodium phosphate buffer develop a transmembrane electric potential during respiration. The magnitude of this potential was determined by three independent methods: (i) fluorescence of 3,3'-dipropylthiodicarbocyanine and 3,3'-dihexyloxacarbocyanine; (ii) uptake of 86Rb+ in the presence of valinomycin; and (iii) uptake of [3H]triphenylmethyl phosphonium. In method (i), the relative fluorescence of these cyanine dyes in the presence of intact cells or derived vesicles is quenched during oxication of electron donors. A linear relationship between this quenching and a potassium diffusion potential was employed to calibrate the probe response. In method (ii), the steady-state concentration ratio of rubidium across the vesicle membrane during oxidation of L-malate was converted to potential by the Nernst equation. In method (iii), the steady-state concentration ratio of this lipophilic cation was likewise converted to a potential. With the exception of 3,3'-dihexyloxacarbocyanine fluorescence, these methods gave good agreement for the potential developed during L-malate oxidation by membrane vesicles. A value of 75 to 80 mV (inside negative) was obtained for vesicles prepared in potassium phosphate, and 104 mV (inside negative) was obtained for vesicles prepared in sodium phosphate. Electrogenic expulsion of hydrogen ion was observed during L-malate oxidation, and the amount of proton exodus was greater in potassium rather than the sodium-containing vesicles. This indicates the presence of a sodium-proton antiport mechanism. In addition, D-glucose uptake was observed during development of a potassium diffusion potential that was artificially imposed across the vesicle membrane. These observations suggest the presence of a glucose-proton symport mechanism in accordance with the principles of Mitchell.
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- Altendorf K., Hirata H., Harold F. M. Accumulation of lipid-soluble ions and of rubidium as indicators of the electrical potential in membrane vesicles of Escherichia coli. J Biol Chem. 1975 Feb 25;250(4):1405–1412. [PubMed] [Google Scholar]
- Bakeeva L. E., Grinius L. L., Jasaitis A. A., Kuliene V. V., Levitsky D. O., Liberman E. A., Severina I. I., Skulachev V. P. Conversion of biomembrane-produced energy into electric form. II. Intact mitochondria. Biochim Biophys Acta. 1970 Aug 4;216(1):13–21. doi: 10.1016/0005-2728(70)90154-4. [DOI] [PubMed] [Google Scholar]
- Barnes E. M., Jr Glucose transport in membrane vesicles from Azotobacter vinelandii. Arch Biochem Biophys. 1974 Jul;163(1):416–422. doi: 10.1016/0003-9861(74)90493-7. [DOI] [PubMed] [Google Scholar]
- Barnes E. M., Jr Multiple sites for coupling of glucose transport to the respiratory chain of membrane vesicles from Azotobacter vinelandii. J Biol Chem. 1973 Dec 10;248(23):8120–8124. [PubMed] [Google Scholar]
- Griniuviene B., Chmieliauskaite V., Melvydas V., Dzheja P., Grinius L. Conversion of Escherichia coli cell-produced metabolic energy into electric form. J Bioenerg. 1975 Mar;7(1):17–38. doi: 10.1007/BF01558460. [DOI] [PubMed] [Google Scholar]
- Hoffman J. F., Laris P. C. Determination of membrane potentials in human and Amphiuma red blood cells by means of fluorescent probe. J Physiol. 1974 Jun;239(3):519–552. doi: 10.1113/jphysiol.1974.sp010581. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kashket E. R., Wilson T. H. Protonmotive force in fermenting Streptococcus lactis 7962 in relation to sugar accumulation. Biochem Biophys Res Commun. 1974 Aug 5;59(3):879–886. doi: 10.1016/s0006-291x(74)80061-6. [DOI] [PubMed] [Google Scholar]
- Laris P. C., Pershadsingh H. A. Estimations of membrane potentials in Streptococcus faecalis by means of a fluorescent probe. Biochem Biophys Res Commun. 1974 Apr 8;57(3):620–626. doi: 10.1016/0006-291x(74)90591-9. [DOI] [PubMed] [Google Scholar]
- Mitchell P. Performance and conservation of osmotic work by proton-coupled solute porter systems. J Bioenerg. 1973 Jan;4(1):63–91. doi: 10.1007/BF01516051. [DOI] [PubMed] [Google Scholar]
- Rottenberg H., Grunwald T., Avron M. Determination of pH in chloroplasts. I. Distribution of ( 14 C) methylamine. Eur J Biochem. 1972 Jan 31;25(1):54–63. doi: 10.1111/j.1432-1033.1972.tb01666.x. [DOI] [PubMed] [Google Scholar]
- Schuldiner S., Kaback H. R. Membrane potential and active transport in membrane vesicles from Escherichia coli. Biochemistry. 1975 Dec 16;14(25):5451–5461. doi: 10.1021/bi00696a011. [DOI] [PubMed] [Google Scholar]
- Sims P. J., Waggoner A. S., Wang C. H., Hoffman J. F. Studies on the mechanism by which cyanine dyes measure membrane potential in red blood cells and phosphatidylcholine vesicles. Biochemistry. 1974 Jul 30;13(16):3315–3330. doi: 10.1021/bi00713a022. [DOI] [PubMed] [Google Scholar]