Low resolution structure of a bacterial SLC26 transporter reveals dimeric stoichiometry and mobile intracellular domains

Emma Compton-Daw, Eleni Karinou, James H. Naismith, Frank Gabel, Arnaud Javelle

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The SLC26/SulP (solute carrier/sulfate transporter) proteins are a superfamily of anion transporters conserved from bacteria to man, of which four have been identified in human diseases. Proteins within the SLC26/SulP family exhibit a wide variety of functions, transporting anions from halides to carboxylic acids. The proteins comprise a transmembrane domain containing between 10-12 transmembrane helices followed a by C-terminal cytoplasmic sulfate transporter and anti-sigma factor antagonist (STAS) domain. These proteins are expected to undergo conformational changes during the transport cycle; however, structural information for this family remains sparse, particularly for the full-length proteins. To address this issue, we conducted an expression and detergent screen on bacterial Slc26 proteins. The screen identified a Yersinia enterocolitica Slc26A protein as the ideal candidate for further structural studies as it can be purified to homogeneity. Partial proteolysis, co-purification, and analytical size exclusion chromatography demonstrate that the protein purifies as stable oligomers. Using small angle neutron scattering combined with contrast variation, we have determined the first low resolution structure of a bacterial Slc26 protein without spectral contribution from the detergent. The structure confirms that the protein forms a dimer stabilized via its transmembrane core; the cytoplasmic STAS domain projects away from the transmembrane domain and is not involved in dimerization. Supported by additional biochemical data, the structure suggests that large movements of the STAS domain underlie the conformational changes that occur during transport.

Original languageEnglish
Pages (from-to)27058-27067
Number of pages10
JournalJournal of Biological Chemistry
Volume286
Issue number30
DOIs
Publication statusPublished - 29 Jul 2011

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Keywords

  • anion transport proteins
  • bacterial proteins
  • crystallography, x-ray
  • humans
  • ion transport
  • protein multimerization
  • protein structure, quaternary
  • protein structure, tertiary
  • yersinia enterocolitica

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