K+/H+ antiport in mitochondria.
Mitochondria contain a latent K+/H+ antiporter that is activated by Mg2+-depletion and shows optimal activity in alkaline, hypotonic suspending media. This K+/H+ antiport activity appears responsible for a respiration-dependent extrusion of endogenous K+, for passive swelling in K+ acetate and other media, for a passive exchange of matrix 42K+ against external K+, Na+, or Li+, and for the respiration-dependent ion extrusion and osmotic contraction of mitochondria swollen passively in K+ nitrate. K+/H+ antiport is inhibited by quinine and by dicyclohexylcarbodiimide when this reagent is reacted with Mg2+-depleted mitochondria. There is good suggestive evidence that the K+/H+ antiport may serve as the endogenous K+-extruding device of the mitochondrion. There is also considerable experimental support for the concept that the K+/H+ antiport is regulated to prevent futile influx-efflux cycling of K+. However, it is not yet clear whether such regulation depends on matrix free Mg2+, on membrane conformational changes, or other as yet unknown factors.
Brierley
G P
GP
Department of Physiological Chemistry, Ohio State University Medical Center, Columbus 43210.
Jung
D W
DW
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D066298:In Vitro Techniques; D008928:Mitochondria / Q000378:metabolism*; D008933:Mitochondrial Swelling; D011188:Potassium / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters
D002352:Carrier Proteins; D027961:Potassium-Hydrogen Antiporters; D006859:Hydrogen; D011188:Potassium