The Proton Permeability of Liposomes Made from Mitochondrial Inner Membrane Phospholipids: Comparison with Isolated Mitochondria

The Proton Permeability of Liposomes Made from Mitochondrial Inner Membrane Phospholipids:... Unilamellar liposomes with native phospholipid fatty acid composition were prepared from rat liver mitochondrial inner membrane phospholipids by extrusion in medium containing 50 mm potassium. They were diluted into low potassium medium to establish a transmembrane potassium gradient. A known membrane potential was imposed by addition of valinomycin, and proton flux into liposomes was measured. Valinomycin in the range 10 pm–1nm was sufficient to fully establish membrane potential. Valinomycin concentrations above 3 nm catalyzed additional proton flux and were avoided. At 300 pm valinomycin, proton flux depended nonlinearly on membrane potential. At 160 mV membrane potential the flux was 30 nmol H+/min/mg phospholipid—approximately 5% of the proton leak flux under comparable conditions in isolated mitochondria, indicating that leak pathways through bulk phospholipid bilayer account for only a small proportion of total mitochondrial proton leak. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Proton Permeability of Liposomes Made from Mitochondrial Inner Membrane Phospholipids: Comparison with Isolated Mitochondria

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1997 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900168
Publisher site
See Article on Publisher Site

Abstract

Unilamellar liposomes with native phospholipid fatty acid composition were prepared from rat liver mitochondrial inner membrane phospholipids by extrusion in medium containing 50 mm potassium. They were diluted into low potassium medium to establish a transmembrane potassium gradient. A known membrane potential was imposed by addition of valinomycin, and proton flux into liposomes was measured. Valinomycin in the range 10 pm–1nm was sufficient to fully establish membrane potential. Valinomycin concentrations above 3 nm catalyzed additional proton flux and were avoided. At 300 pm valinomycin, proton flux depended nonlinearly on membrane potential. At 160 mV membrane potential the flux was 30 nmol H+/min/mg phospholipid—approximately 5% of the proton leak flux under comparable conditions in isolated mitochondria, indicating that leak pathways through bulk phospholipid bilayer account for only a small proportion of total mitochondrial proton leak.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 15, 1997

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