title: Stoichiometry and arrangement of subunits in rod cyclic nucleotide-gated channels.
abstract: Cyclic nucleotide-gated (CNG) ion channels mediate the response to light in retinal rods. They are tetramers of two homologous subunits (alpha and beta), each of which is essential for the function of the channels in vivo. We have investigated the stoichiometry and arrangement of these two subunits to determine how they come together within an individual channel complex. We exploited the very specific geometric and spatial requirements for forming a high-affinity Ni2+-binding site to examine the number and relative positions of the subunits. We found that only an order of alpha/alpha/beta/beta could account qualitatively and quantitatively for the observed intersubunit coordination of Ni2+ in wild-type and mutant alpha/beta channels. Furthermore, our results suggest a structural dimerization among like subunits, at least at the level of the Ni2+-binding site.
authors.affiliation: Department of Ophthalmology, University of Washington School of Medicine, Seattle 98195, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: Shammat
authors.forename: S E
authors.initials: SE
authors.lastname: Gordon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D000242:Cyclic AMP / Q000502:physiology*; D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins / Q000096:biosynthesis / Q000235:genetics; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D007473:Ion Channels / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D009532:Nickel / Q000378:metabolism / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012374:Rod Cell Outer Segment / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins; D007473:Ion Channels; D009532:Nickel; D000242:Cyclic AMP