Properties of the inner membrane anion channel in intact mitochondria.
The mitochondrial inner membrane possesses an anion channel (IMAC) which mediates the electrophoretic transport of a wide variety of anions and is believed to be an important component of the volume homeostatic mechanism. IMAC is regulated by matrix Mg2+ (IC50 = 38 microM at pH 7.4) and by matrix H+ (pIC50 = 7.7). Moreover, inhibition by Mg2+ is pH-dependent. IMAC is also reversibly inhibited by many cationic amphiphilic drugs, including propranolol, and irreversibly inhibited by N,N'-dicyclohexylcarbodiimide. Mercurials have two effects on its activity: (1) they increase the IC50 values for Mg2+, H+, and propranolol, and (2) they inhibit transport. The most potent inhibitor of IMAC is tributyltin, which blocks anion uniport in liver mitochondria at about 1 nmol/mg. The inhibitory dose is increased by mercurials; however, this effect appears to be unrelated to the other mercurial effects. IMAC also appears to be present in plant mitochondria; however, it is insensitive to inhibition by Mg2+, mercurials, and N,N'-dicyclohexylcarbodiimide. Some inhibitors of the adenine nucleotide translocase also inhibit IMAC, including Cibacron Blue, agaric acid, and palmitoyl CoA; however, atractyloside has no effect.
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Department of Pharmacology, Medical College of Ohio, Toledo 43699-0008.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D005033:Ethylmaleimide / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008628:Mercury / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D018272:Porins; D050994:Voltage-Dependent Anion Channels
D007473:Ion Channels; D008565:Membrane Proteins; D018272:Porins; D050994:Voltage-Dependent Anion Channels; D000255:Adenosine Triphosphate; D008628:Mercury; D005033:Ethylmaleimide