The K+ conductance of the inner mitochondrial membrane. A study of the inducible uniport for monovalent cations.
Addition of A23187 plus EDTA to rat liver mitochondria induces a common uniport pathway for monovalent cations. In this study, we have carried out a detailed characterization of the flow/force relationship for K+ transport along this pathway under steady state conditions. In the presence of EDTA, the K+ conductance is a linear function of external K+ in the range 0-20 mM K+, with a slope of 0.15 nmol of K+ x mg of protein-1 x min-1 x mV-1. The K+ conductance is inhibited by Mg2+ in the range 10(-9)-10(-6) M, while K+ flux is stimulated by the sulfhydryl group reagent mersalyl. Uniport activity can be detected in native mitochondria. These findings are compatible with the notion that electrophoretic K+ flux across the inner membrane takes place via a regulated K+ uniport with the potential of transporting K+ at rates in excess of 600 nmol x mg of protein-1 x min-1.
Nicolli
A
A
Consiglio Nazionale delle Ricerche Unit for the Study of Physiology of Mitochondria, University of Padova, Italy.
Redetti
A
A
Bernardi
P
P
D000818:Animals; D001692:Biological Transport; D000001:Calcimycin / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004492:Edetic Acid / Q000737:chemistry; D004553:Electric Conductivity; D008274:Magnesium / Q000737:chemistry; D008564:Membrane Potentials; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009550:Nigericin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011803:Quinine / Q000494:pharmacology; D051381:Rats
D002412:Cations; D000001:Calcimycin; D004492:Edetic Acid; D011803:Quinine; D008274:Magnesium; D009550:Nigericin; D011188:Potassium