Regulation of mitochondrial KATP channel by redox agents.
The ATP-dependent K+ channel (KATP) was purified from the inner mitochondrial membrane and reconstituted into lipid bilayer membranes. KATP activity was inhibited by high concentrations of ATP and ADP, but activated by low concentrations (up to 200 microM) of ADP. p-Diethylaminoethylbenzoate (DEB) acted as a KATP opener: at micromolar concentrations, it reversed inhibition by ATP and ADP and it also prevented KATP rundown. Pelargonidine, extracted from flowers of Pelargonium, reduced spontaneous activity of KATP channels and diminished their potentiation by DEB. Their opposite action on KATP corresponded with their opposite redox properties in reactions with free radicals: DEB behaved as an electron donor, whereas pelargonidine acted as an electron acceptor. We hypothesize that thiol groups on mitoKATP are targets for redox-active ligans.