title: A secondary structural transition in the C-helix promotes gating of cyclic nucleotide-regulated ion channels.
abstract: Cyclic nucleotide-regulated ion channels bind second messengers like cAMP to a C-terminal domain, consisting of a β-roll, followed by two α-helices (B- and C-helices). We monitored the cAMP-dependent changes in the structure of the C-helix of a C-terminal fragment of HCN2 channels using transition metal ion FRET between fluorophores on the C-helix and metal ions bound between histidine pairs on the same helix. cAMP induced a change in the dimensions of the C-helix and an increase in the metal binding affinity of the histidine pair. cAMP also caused an increase in the distance between a fluorophore on the C-helix and metal ions bound to the B-helix. Stabilizing the C-helix of intact CNGA1 channels by metal binding to a pair of histidines promoted channel opening. These data suggest that ordering of the C-helix is part of the gating conformational change in cyclic nucleotide-regulated channels.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195-7290, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Puljung
authors.forename: William N
authors.initials: WN
authors.lastname: Zagotta
mesh_terms: D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport / Q000502:physiology; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D015221:Potassium Channels; D055550:Protein Stability; D017433:Protein Structure, Secondary
chemical_list: C518242:Cnga1 protein, mouse; D054815:Cyclic Nucleotide-Gated Cation Channels; C578711:Hcn2 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D008670:Metals; D015221:Potassium Channels; D000242:Cyclic AMP
keywords: Allosteric Regulation; Cyclic AMP (cAMP); Fluorescence; Fluorescence Resonance Energy Transfer (FRET); Ion Channels