Functional distinctions between the mitochondrial ATP-dependent K+ channel (mitoKATP) and its inward rectifier subunit (mitoKIR).
The ATP-sensitive potassium channel from the inner mitochondrial membrane (mitoK(ATP)) is a highly selective conductor of K(+) ions. When isolated in the presence of nonionic detergent and reconstituted in liposomes, mitoK(ATP) is inhibited with high affinity by ATP (K((1/2)) = 20-30 microM). We have suggested that holo-mitoK(ATP) is a heteromultimer consisting of an inwardly rectifying K(+) channel (mitoKIR) and a sulfonylurea receptor (Grover, G. J., and Garlid, K. D. (2000) J. Mol. Cell. Cardiol. 32, 677-695). Here, we show that a 55-kDa protein isolated by ethanol extraction and reconstituted in bilayer lipid membranes and liposomes is the mitoKIR. This protein, which lacks the sulfonylurea receptor subunit, is inhibited with low affinity by ATP, with K(1/2) approximately 550 microM. ATP inhibition of both mitoKIR and holo-mitoK(ATP) is reversed by UDP (K((1/2))1/2 = 10-15 microM). Holo-mitoK(ATP) is and diazoxide, and the opened by cromakalim flux through the open channel is inhibited by glibenclamide and 5-hydroxydecanoate. None of these agents has any effect upon mitoKIR. We have identified two compounds that act specifically on mitoKIR. p-diethylaminoethylbenzoate reverses inhibition of mitoKIR by ATP and ADP at micromolar concentrations and also opens mitoK(ATP) in isolated mitochondria. Tetraphenylphosphonium inhibits K(+) flux through both mitoKIR and mitoK(ATP) with the same apparent affinity. These findings support the hypothesis that the 55-kDa mitoKIR is the channel component of mitoK(ATP).
Mironova
Galina D
GD
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
Negoda
Alexandr E
AE
Marinov
Benjamin S
BS
Paucek
Petr
P
Costa
Alexandre D T
AD
Grigoriev
Serguey M
SM
Skarga
Yuri Yu
YY
Garlid
Keith D
KD
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D001921:Brain / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D007477:Ions; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008274:Magnesium / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D051381:Rats; D011955:Receptors, Drug / Q000737:chemistry / Q000378:metabolism; D064233:Sulfonylurea Receptors; D013997:Time Factors; D014530:Uridine Diphosphate / Q000378:metabolism
C117781:4-diethylaminoethylbenzoate; D018528:ATP-Binding Cassette Transporters; D001565:Benzoates; D007477:Ions; D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; C117780:mitochondrial K(ATP) channel; D014530:Uridine Diphosphate; D000255:Adenosine Triphosphate; D008274:Magnesium; D011188:Potassium