title: Stoichiometry and specific assembly of Best ion channels.
abstract: Human Bestrophin 1 (hBest1) is a calcium-activated chloride channel that regulates neuronal excitability, synaptic activity, and retinal homeostasis. Mutations in hBest1 cause the autosomal-dominant Best macular dystrophy (BMD). Because hBest1 mutations cause BMD, but a knockout does not, we wondered if hBest1 mutants exert a dominant negative effect through interaction with other calcium-activated chloride channels, such as hBest2, 3, or 4, or transmembrane member 16A (TMEM16A), a member of another channel family. The subunit architecture of Best channels is debated, and their ability to form heteromeric channel assemblies is unclear. Using single-molecule subunit analysis, we find that each of hBest1, 2, 3, and 4 forms a homotetrameric channel. Despite considerable conservation among hBests, hBest1 has little or no interaction with other hBests or mTMEM16A. We identify the domain responsible for assembly specificity. This domain also plays a role in channel function. Our results indicate that Best channels preferentially self-assemble into homotetramers.
authors.affiliation: Department of Molecular and Cell Biology, and Helen Wills Neuroscience Graduate Program, University of California, Berkeley, CA 94720.
authors.forename: Shashank
authors.initials: S
authors.lastname: Bharill
authors.forename: Zhu
authors.initials: Z
authors.lastname: Fu
authors.forename: Raz
authors.initials: R
authors.lastname: Palty
authors.forename: Ehud Y
authors.initials: EY
authors.lastname: Isacoff
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001681:Biological Assay; D018118:Chloride Channels / Q000737:chemistry / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007454:Iodides / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014981:Xenopus
chemical_list: D018118:Chloride Channels; D007454:Iodides; D021122:Protein Subunits; D011994:Recombinant Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins
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