The Proton Permeability of Liposomes Made from Mitochondrial Inner Membrane Phospholipids: Comparison with Isolated Mitochondria |
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Authors: | PS Brookes DFS Rolfe MD Brand |
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Institution: | (1) Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW, United Kingdom, GB |
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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.
Received: 5 August 1996/Revised: 1 October 1996 |
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Keywords: | : Mitochondria — Vesicle — Proton leak — Phospholipid — Liposome — Fatty acid |
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