title: Structural diversity in the cytoplasmic region of G protein-gated inward rectifier K+ channels.
abstract: Inward rectifier K+ (Kir) channels can be functionally categorized into two groups: those that are constitutively active and those that are constitutively inactive, with examples such as Kir2.x and Kir3.x, respectively. Their cytoplasmic regions are thought to be critical for control of channel gating, but a structural basis for this hypothesis is not known. In this study, we report a structure for the cytoplasmic region of a G protein-gated Kir channel, Kir3.2, and compare it with those of Kir3.1 and Kir2.1 channels. The isolated cytoplasmic region of Kir3.2 forms a tetrameric assembly in solution and also in the crystal. While the secondary structure arrangement and the subunit interface of the Kir3.2 crystal structure are found to be nearly identical to those of Kir3.1 and Kir2.1, it is quite different at and around loops between betaC- and betaD-strands and between betaH- and betaI-strands. These structural elements are located at the interface with the plasma membrane. Therefore, these structural elements could associate with the Kir channel transmembrane helices and be involved in the regulation of Kir channel gating.
authors.affiliation: Division of Molecular and Cellular Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Inanobe
authors.forename: Takanori
authors.initials: T
authors.lastname: Matsuura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Kurachi
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015640:Ion Channel Gating / Q000502:physiology*; D051379:Mice; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C497069:Kcnj6 protein, mouse; C489461:Kir2.1 channel; D024661:Potassium Channels, Inwardly Rectifying; D019204:GTP-Binding Proteins