title: Homologue structure of the SLAC1 anion channel for closing stomata in leaves.
abstract: The plant SLAC1 anion channel controls turgor pressure in the aperture-defining guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought or high levels of carbon dioxide. Here we determine the crystal structure of a bacterial homologue (Haemophilus influenzae) of SLAC1 at 1.20 Å resolution, and use structure-inspired mutagenesis to analyse the conductance properties of SLAC1 channels. SLAC1 is a symmetrical trimer composed from quasi-symmetrical subunits, each having ten transmembrane helices arranged from helical hairpin pairs to form a central five-helix transmembrane pore that is gated by an extremely conserved phenylalanine residue. Conformational features indicate a mechanism for control of gating by kinase activation, and electrostatic features of the pore coupled with electrophysiological characteristics indicate that selectivity among different anions is largely a function of the energetic cost of ion dehydration.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
authors.forename: Yu-Hang
authors.initials: YH
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Hu
authors.forename: Marco
authors.initials: M
authors.lastname: Punta
authors.forename: Renato
authors.initials: R
authors.lastname: Bruni
authors.forename: Brandan
authors.initials: B
authors.lastname: Hillerich
authors.forename: Brian
authors.initials: B
authors.lastname: Kloss
authors.forename: Burkhard
authors.initials: B
authors.lastname: Rost
authors.forename: James
authors.initials: J
authors.lastname: Love
authors.forename: Steven A
authors.initials: SA
authors.lastname: Siegelbaum
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Hendrickson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D004553:Electric Conductivity; D006193:Haemophilus influenzae / Q000737:chemistry* / Q000235:genetics; D015640:Ion Channel Gating; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism*; D055672:Static Electricity; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D014982:Xenopus laevis
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; C528438:SLAC1 protein, Arabidopsis; D010649:Phenylalanine