A region of the sulfonylurea receptor critical for a modulation of ATP-sensitive K+ channels by G-protein βγ-subunits

To determine the interaction site(s) of ATP-sensitive K+ (KATP) channels for G-proteins, sulfonylurea receptor (SUR2A or SUR1) and pore-forming (Kir6.2) subunits were reconstituted in the mammalian cell line, COS-7. Intracellular application of the G-protein βγ2-subunits (Gβγ2) caused a reduction of ATP-induced inhibition of Kir6.2/SUR channel activities by lessening the ATP sensitivity of the channels. Gβγ2 bound in vitro to both intracellular (loop-NBD) and C-terminal segments of SUR2A, each containing a nucleotide-binding domain (NBD). Furthermore, a single amino acid substitution in the loop-NBD of SUR (Arg656Ala in SUR2A or Arg665Ala in SUR1) abolished the Gβγ2-dependent alteration of the channel activities. These findings provide evidence that Gβγ modulates KATP channels through a direct interaction with the loop-NBD of SUR.