title: Inward rectifier potassium channel Kir 2.3 is inhibited by internal sulfhydryl modification.
abstract: Regions of the hippocampal inward rectifier potassium channel Kir 2.3 that contact the aqueous environment were investigated by identification of native cysteine residues that confer sulfhydryl reagent sensitivity to the channel conductance. Kir 2.3 currents were inhibited by N-ethylmaleimide (NEM), whereas currents of Kir 2.1 were unaffected. The reactive residues were identified as Kir 2.3 Cys28 and Cys50 using chimeric constructs and mutagenesis. These sites were not accessible to p-chloromercuriphenylsulfonate (pCMPS) applied extracellularly. However, both Cys28 and Cys50 were accessible to 2-(trimethylammoniumethyl) methanethiosulfonate (MTSET) applied to the intracellular surface of the membrane. These studies demonstrate that Cys28 and Cys50 lie in a cytoplasmic aqueous accessible region of the channel, and suggest that the channel N-terminus is a key constituent of the internal vestibule of the pore and/or modulates channel gating.
authors.affiliation: Neuroscience Research Institute, Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara 93106, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Radeke
authors.forename: L R
authors.initials: LR
authors.lastname: Conti
authors.forename: C A
authors.initials: CA
authors.lastname: Vandenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D003545:Cysteine / Q000737:chemistry*; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D014981:Xenopus
chemical_list: C099489:KCNJ4 protein, human; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D013439:Sulfhydryl Reagents; D006859:Hydrogen; D004247:DNA; D003545:Cysteine