Open AccessThe Effective Proton Conductance of the Inner Membrane of Mitochondria from Brown Adipose Tissue
Author(s) -
NICHOLLS David G.
Publication year - 1977
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1977.tb11674.x
Subject(s) - conductance , chemistry , brown adipose tissue , membrane , proton , membrane potential , nucleotide , pi , phosphate , biophysics , biochemistry , adipose tissue , biology , physics , quantum mechanics , mathematics , combinatorics , gene
The nucleotide‐sensitive H + (OH − ) conducting pathway of mitochondria from the brown‐adipose tissue of cold‐adapted guinea‐pigs passes an effective proton current which is directly proportional to the proton electrochemical gradient. At 23 ° C and pH 7.0 this conductance is 16 nmol H + · min −1 · mg −1 · mV −1 . Addition of 0.2 mM GDP results in a conductance which is linear and low (0.7 nmol H + · min −1 · mg −1 · mV −1 ) until Δ H + exceeds 220 mV. At higher values of Δ H +, which can be attained by glycerol 3‐phosphate oxidation but not palmitoyl‐ L ‐carnitine plus malate oxidation, the membrane conductance greatly increases, effectively limiting the maximal Δ H + to 240 mV. High glycerol 3‐phosphate concentrations which have the thermodynamic potential to exceed this value of Δ H + instead create a greatly increased rate of controlled respiration. The generality and significance of this device to limit Δ H +, and its relation to the nucleotide‐sensitive conductance, are discussed.