title: Novel nucleotide-binding sites in ATP-sensitive potassium channels formed at gating interfaces.
abstract: The coupling of cell metabolism to membrane electrical activity is a vital process that regulates insulin secretion, cardiac and neuronal excitability and the responses of cells to ischemia. ATP-sensitive potassium channels (K(ATP); Kir6.x) are a major part of this metabolic-electrical coupling system and translate metabolic signals such as the ATP:ADP ratio to changes in the open or closed state (gate) of the channel. The localization of the nucleotide-binding site (NBS) on Kir6.x channels and how nucleotide binding gates these K(ATP) channels remain unclear. Here, we use fluorescent nucleotide binding to purified Kir6.x proteins to define the peptide segments forming the NBS on Kir6.x channels and show that unique N- and C-terminal interactions from adjacent subunits are required for high-affinity nucleotide binding. The short N- and C-terminal segments comprising the novel intermolecular NBS are next to helices that likely move with channel opening/closing, suggesting a lock-and-key model for ligand gating.
authors.affiliation: Department of Cellular and Molecular Physiology, School of Medicine, Yale University, New Haven, CT, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Dong
authors.forename: Lie-Qi
authors.initials: LQ
authors.lastname: Tang
authors.forename: Gordon G
authors.initials: GG
authors.lastname: MacGregor
authors.forename: Qiang
authors.initials: Q
authors.lastname: Leng
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hebert
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D008024:Ligands; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009711:Nucleotides / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation; D016415:Sequence Alignment; D014982:Xenopus laevis; D000099161:Kcnj11 Channel
chemical_list: D000255:Adenosine Triphosphate; D018076:DNA, Complementary; D008024:Ligands; D009711:Nucleotides; D019269:Phosphatidylinositol 4,5-Diphosphate; D024661:Potassium Channels, Inwardly Rectifying; D000099161:Kcnj11 Channel; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate