Pharmacological Characterization of a Recombinant Mitochondrial ROMK2 Potassium Channel Expressed in Bacteria and Reconstituted in Planar Lipid Bilayers

In the inner mitochondrial membrane, several potassium channels that play a role in cell life and death have been identified. One of these channels is the ATP-regulated potassium channel (mitoK(ATP)). The ROMK2 potassium channel is a potential molecular component of the mitoK(ATP) channel. The current study aimed to investigate the pharmacological modulation of the activity of the ROMK2 potassium channel expressed in Escherichia coli bacteria. ROMK2 was solubilized in polymer nanodiscs and incorporated in planar lipid bilayers. The impact of known mitoK(ATP) channel modulators on the activity of the ROMK2 was characterized. We found that the ROMK2 channel was activated by the mitoK(ATP) channel opener diazoxide and blocked by mitoK(ATP) inhibitors such as ATP/Mg(2+), 5-hydroxydecanoic acid, and antidiabetic sulfonylurea glibenclamide. These results indicate that the ROMK2 potassium protein may be a pore-forming subunit of mitoK(ATP) and that the impact of channel modulators is not related to the presence of accessory proteins.