CHEMICAL MODIFICATION OF ARGININES BY 2,3-BUTANEDIONE AND PHENYLGLYOXAL CAUSES CLOSURE OF THE MITOCHONDRIAL PERMEABILITY TRANSITION PORE

We have investigated the role of arginine residues in the regulation o f the mitochondrial permeability transition pore, a cyclosporin A-sens itive inner membrane channel. Isolated rat liver mitochondria were tre ated with the arginine-specific chemical reagent 2,3-butanedione or ph enylglyoxal, followed by removal of excess free reagent. After this tr eatment, mitochondria accumulated Ca2+ normally, but did not undergo p ermeability transition following depolarization, a condition that norm ally triggers opening of the permeability transition pore. Inhibition by 2,3-butanedione and phenylglyoxal correlated with matrix pH, sugges ting that the relevant arginine(s) are exposed to the matrix aqueous p hase. Inhibition by 2,3-butanedione was potentiated by berate and was reversed upon its removal, whereas inhibition by phenylglyoxal was irr eversible. Treatment with 2,3-butanedione or phenylglyoxal after induc tion of the permeability transition by Ca2+ overload resulted in pore closure despite the presence of 0.5 mM Ca2+. At concentrations that we re fully effective at inhibiting the permeability transition, these ar ginine reagents (i) had no effect on the isomerase activity of cycloph ilin D and (ii) did not affect the rate of ATP translocation and hydro lysis, as measured by the production of a membrane potential upon ATP addition in the presence of rotenone, We conclude that reaction with 2 ,3-butanedione and phenylglyoxal results in a stable chemical modifica tion of critical arginine residue(s) located on the matrix side of the inner membrane, which, in turn, strongly favors a closed state of the pore.