Remodelling of the SUR-Kir6.2 interface of the KATP channel upon ATP binding revealed by the conformational blocker rhodamine 123.
ATP-sensitive K+ channels (K(ATP) channels) are metabolic sensors formed by association of a K+ channel, Kir6, and an ATP-binding cassette (ABC) protein, SUR, which allosterically regulates channel gating in response to nucleotides and pharmaceutical openers and blockers. How nucleotide binding to SUR translates into modulation of Kir6 gating remains largely unknown. To address this issue, we have used a novel conformational KATP channel inhibitor, rhodamine 123 (Rho123) which targets the Kir6 subunit in a SUR-dependent manner. Rho123 blocked SUR-less Kir6.2 channels with an affinity of approximately 1 microM, regardless of the presence of nucleotides, but it had no effect on channels formed by the association of Kir6.2 and the N-terminal transmembrane domain TMD0 of SUR. Rho123 blocked SUR + Kir6.2 channels with the same affinity as Kir6.2 but this effect was antagonized by ATP. Protection from Rho123 block by ATP was due to direct binding of ATP to SUR and did not entail hydrolysis because it was not mimicked by AMP, did not require Mg2+ and was reduced by mutations in the nucleotide-binding domains of SUR. These results suggest that Rho123 binds at the TMD0-Kir6.2 interface and that binding of ATP to SUR triggers a change in the structure of the contact zone between Kir6.2 and domain TMD0 of SUR that causes masking of the Rho123 site on Kir6.2.
Hosy
Eric
E
Institute of Structural Biology, UMR5075 CEA-CNRS-University J. Fourier, 41, rue Jules Horowitz, 38027 Grenoble, France.
Dérand
Renaud
R
Revilloud
Jean
J
Vivaudou
Michel
M
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D001667:Binding, Competitive; D003001:Cloning, Molecular; D006224:Cricetinae; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009154:Mutation; D009865:Oocytes; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000378:metabolism / Q000494:pharmacology*; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D051381:Rats; D011955:Receptors, Drug / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020112:Rhodamine 123 / Q000378:metabolism / Q000494:pharmacology*; D064233:Sulfonylurea Receptors; D013997:Time Factors; D014982:Xenopus laevis; D000099161:Kcnj11 Channel
D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate; D005456:Fluorescent Dyes; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D020112:Rhodamine 123; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel