title: Structural model of the anion exchanger 1 (SLC4A1) and identification of transmembrane segments forming the transport site.
abstract: The anion exchanger 1 (AE1), a member of bicarbonate transporter family SLC4, mediates an electroneutral chloride/bicarbonate exchange in physiological conditions. However, some point mutations in AE1 membrane-spanning domain convert the electroneutral anion exchanger into a Na(+) and K(+) conductance or induce a cation leak in a still functional anion exchanger. The molecular determinants that govern ion movement through this transporter are still unknown. The present study was intended to identify the ion translocation pathway within AE1. In the absence of a resolutive three-dimensional structure of AE1 membrane-spanning domain, in silico modeling combined with site-directed mutagenesis experiments was done. A structural model of AE1 membrane-spanning domain is proposed, and this model is based on the structure of a uracil-proton symporter. This model was used to design cysteine-scanning mutagenesis on transmembrane (TM) segments 3 and 5. By measuring AE1 anion exchange activity or cation leak, it is proposed that there is a unique transport site comprising TM3-5 and TM8 that should function as an anion exchanger and a cation leak.
authors.affiliation: From the Université Nice Sophia Antipolis, Institut de Biologie Valrose, UMR7277, 06100 Nice, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Barneaud-Rocca
authors.forename: Catherine
authors.initials: C
authors.lastname: Etchebest
authors.forename: Hélène
authors.initials: H
authors.lastname: Guizouarn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry*; D000838:Anions / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D008094:Lithium / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes; D017354:Point Mutation; D011188:Potassium / Q000737:chemistry; D017434:Protein Structure, Tertiary; D012964:Sodium / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D014982:Xenopus laevis
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions; C454201:SLC4A1 protein, human; D013438:Sulfhydryl Compounds; D008094:Lithium; D012964:Sodium; D011188:Potassium
keywords: Anion Exchanger 1; Anion Transport; Band 3; Erythrocyte; Homology Modeling; Ion Channels; Protein Structure; SLC4A1