title: Conformational rearrangements in the S6 domain and C-linker during gating in CNGA1 channels.
abstract: This work completes previous findings and, using cysteine scanning mutagenesis (CSM) and biochemical methods, provides detailed analysis of conformational changes of the S6 domain and C-linker during gating of CNGA1 channels. Specific residues between Phe375 and Val424 were mutated to a cysteine in the CNGA1 and CNGA1(cys-free) background and the effect of intracellular Cd(2+) or cross-linkers of different length in the open and closed state was studied. In the closed state, Cd(2+) ions inhibited mutant channels A406C and Q409C and the longer cross-linker reagent M-4-M inhibited mutant channels A406C(cys-free) and Q409C(cys-free). Cd(2+) ions inhibited mutant channels D413C and Y418C in the open state, both constructed in a CNGA1 and CNGA1(cys-free) background. Our results suggest that, in the closed state, residues from Phe375 to approximately Ala406 form a helical bundle with a three-dimensional (3D) structure similar to those of the KcsA; furthermore, in the open state, residues from Ser399 to Gln409 in homologous subunits move far apart, as expected from the gating in K(+) channels; in contrast, residues from Asp413 to Tyr418 in homologous subunits become closer in the open state.
authors.affiliation: International School for Advanced Studies, via Beirut 2-4, 34014, Trieste, Italy.
authors.forename: Anil V
authors.initials: AV
authors.lastname: Nair
authors.forename: Chuong H H
authors.initials: CH
authors.lastname: Nguyen
authors.forename: Monica
authors.initials: M
authors.lastname: Mazzolini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002417:Cattle; D003432:Cross-Linking Reagents / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels; D042541:Intracellular Space / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009068:Movement; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000187:drug effects; D013439:Sulfhydryl Reagents / Q000494:pharmacology
chemical_list: C475741:CNGA1 protein, bovine; D003432:Cross-Linking Reagents; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D013439:Sulfhydryl Reagents; D002104:Cadmium