Anion uniport in plant mitochondria is mediated by a Mg2+-insensitive inner membrane anion channel

It has long been established that the inner membrane of plant mitochondria is permeable to Cl-. Evidence has also accumulated which suggests that a number of other anions such as Pi and dicarboxylates can also be transported electrophoretically. In this paper, we present evidence that anion uniport...

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Bibliographic Details
Published in:The Journal of biological chemistry 1992-02, Vol.267 (5), p.3079-3087
Main Authors: BEAVIS, A. D, VERCESI, A. E
Format: Article
Language:English
Subjects:
anion
aniones
anions
Biological and medical sciences
cell membranes
Cell physiology
Fundamental and applied biological sciences. Psychology
inhibicion
inhibition
ion
iones
ions
magnesio
magnesium
membranas celulares
Membrane and intracellular transports
membrane cellulaire
mitochondria
mitochondrie
mitocondria
Molecular and cellular biology
solanum tuberosum
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Summary:It has long been established that the inner membrane of plant mitochondria is permeable to Cl-. Evidence has also accumulated which suggests that a number of other anions such as Pi and dicarboxylates can also be transported electrophoretically. In this paper, we present evidence that anion uniport in plant mitochondria is mediated via a pH-regulated channel related to the so-called inner membrane anion channel (IMAC) of animal mitochondria. Like IMAC, the channel in potato mitochondria transports a wide variety of anions including NO3-, Cl-, ferrocyanide, 1,2,3-benzene-tricarboxylate, malonate, Pi, alpha-ketoglutarate, malate adipate and glucuronate. In the presence of nigericin, anion uniport is sensitive to the medium pH (pIC5O = 7.60, Hill coefficient = 2). In the absence of nigericin, transport rates are much lower and much less sensitive to pH, suggesting that matrix H+ inhibit anion uniport. This conclusion is supported by measurements of H+ flux which reveal that "activation" of anion transport at high pH by nigericin and at low pH by respiration is associated with an efflux of matrix H+. Other inhibitors of IMAC which are found to block anion uniport in potato mitochondria include propranolol (IC50 = 14 micromole, Hill coefficient = 1.28), tributyltin (IC50 = 4 nmol/mg, Hill coefficient = 2.0), and the nucleotide analogs Erythrosin B and Cibacron Blue 3GA. The channel in plant mitochondria differs from IMAC in that it is not inhibited by matrix Mg2+, mercurials, or N,N'-dicyclohexylcarbodiimide. The lack of inhibition by Mg2+ suggests that the physiological regulation of the plant channel may differ from IMAC and that the plant IMAC may have functions such as a role in the malate/oxaloacetate shuttle in addition to its proposed role in volume homeostasis.
ISSN:0021-9258
1083-351X