title: The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry.
abstract: Cyclic nucleotide-gated (CNG) channels are crucial for visual and olfactory transductions. These channels are tetramers and in their native forms are composed of A and B subunits, with a stoichiometry thought to be 2A:2B (refs 6, 7). Here we report the identification of a leucine-zipper-homology domain named CLZ (for carboxy-terminal leucine zipper). This domain is present in the distal C terminus of CNG channel A subunits but is absent from B subunits, and mediates an inter-subunit interaction. With cross-linking, non-denaturing gel electrophoresis and analytical centrifugation, this CLZ domain was found to mediate a trimeric interaction. In addition, a mutant cone CNG channel A subunit with its CLZ domain replaced by a generic trimeric leucine zipper produced channels that behaved much like the wild type, but less so if replaced by a dimeric or tetrameric leucine zipper. This A-subunit-only, trimeric interaction suggests that heteromeric CNG channels actually adopt a 3A:1B stoichiometry. Biochemical analysis of the purified bovine rod CNG channel confirmed this conclusion. This revised stoichiometry provides a new foundation for understanding the structure and function of the CNG channel family.
authors.affiliation: Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Haining
authors.initials: H
authors.lastname: Zhong
authors.forename: Laurie L
authors.initials: LL
authors.lastname: Molday
authors.forename: Robert S
authors.initials: RS
authors.lastname: Molday
authors.forename: King-Wai
authors.initials: KW
authors.lastname: Yau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002460:Cell Line; D002498:Centrifugation; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents; D054815:Cyclic Nucleotide-Gated Cation Channels; D006801:Humans; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016350:Leucine Zippers / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D051381:Rats; D017948:Retinal Rod Photoreceptor Cells; D013329:Structure-Activity Relationship
chemical_list: D003432:Cross-Linking Reagents; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D021122:Protein Subunits