Identification of an 82,000-dalton protein responsible for K+/H+ antiport in rat liver mitochondria.

Under highly selective conditions, pretreatment of rat liver mitochondria with N,N'-dicyclohexylcarbodiimide (DCCD) results in 95% inhibition of K+/H+ antiport. This inhibition is irreversible. The K+/H+ antiporter is reversibly inhibited by physiological (Mg2+ and H+) and pharmacological (quinine and propranolol) inhibitors. Each of these inhibitors protects the K+/H+ antiporter against inhibition by DCCD. DCCD is without effect on Na+/H+ antiport under all conditions tested, confirming our contention that rat liver mitochondria possess two different alkali cation/proton antiporters (Nakashima, R. A., and Garlid, K. D. (1982) J. Biol. Chem. 257, 9252-9254). The selective nature of irreversible inhibition by DCCD has enabled us to label and identify the protein responsible for K+/H+ antiport. This protein, the first cation antiporter so identified, migrates on sodium dodecyl sulfate-polyacrylamide gels with a molecular weight of 82,000.