title: Hetero-concatemeric KIR6.X4/SUR14 channels display distinct conductivities but uniform ATP inhibition.
abstract: K(IR)6.1 and K(IR)6.2 are the pore-forming subunits of K(NDP)(,) the nucleotide-diphosphate-activated K(ATP) channels, and classical K(ATP) channels, respectively. "Hybrid" channels, in which the structure is predetermined by concatemerizing K(IR)6.1 and K(IR)6.2, exhibit distinct conductivities specified by subunit number and position. Inclusion of one K(IR)6.2 is sufficient to open K(IR)6. X-X-X-X/SUR1(4) in the absence of nucleotide stimulation through sulfonylurea receptor-1 (SUR1). ATP inhibited the spontaneous bursting of hybrid channels with an IC(50(ATP)) approximately 10(-)(5) m, similar to that of K(IR)6.2(4)-containing channels. These findings and a transient increase in K(NDP) channel activity following rapid wash-out of MgATP suggested that K(IR)6.1 is not ATP-insensitive as previously believed. We propose that SUR-dependent, inhibitory ATP-enhanced interactions of the cytoplasmic domains of both K(IR)6.1 and K(IR)6.2 stabilize a closed form of the M2 bundle in the gating apparatus.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA. ababenko@bcm.tmc.edu
authors.forename: A P
authors.initials: AP
authors.lastname: Babenko
authors.forename: G C
authors.initials: GC
authors.lastname: Gonzalez
authors.forename: J
authors.initials: J
authors.lastname: Bryan
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D006801:Humans; D020128:Inhibitory Concentration 50; D015640:Ion Channel Gating / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011955:Receptors, Drug / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D064233:Sulfonylurea Receptors
chemical_list: C577507:ABCC8 protein, human; D018528:ATP-Binding Cassette Transporters; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D021122:Protein Subunits; D011955:Receptors, Drug; D011993:Recombinant Fusion Proteins; D064233:Sulfonylurea Receptors; D000255:Adenosine Triphosphate