The substrate-binding protein imposes directionality on an electrochemical sodium gradient-driven TRAP transporter

Christopher Mulligan, Eric R. Geertsma, Emmanuele Severi, David J. Kelly, Bert Poolman, Gavin H. Thomas

Research output: Contribution to journalArticlepeer-review

Abstract

Substrate-binding protein-dependent secondary transporters are widespread in prokaryotes and are represented most frequently by members of the tripartite ATP-independent periplasmic (TRAP) transporter family. Here, we report the membrane reconstitution of a TRAP transporter, the sialic acid-specific SiaPQM system from Haemophilus influenzae, and elucidate its mechanism of energy coupling. Uptake of sialic acid via membrane-reconstituted SiaQM depends on the presence of the sialic acid-binding protein, SiaP, and is driven by the electrochemical sodium gradient. The interaction between SiaP and SiaQM is specific as transport is not reconstituted using the orthologous sialic acid-binding protein VC1779. Importantly, the binding protein also confers directionality on the transporter, and reversal of sialic acid transport from import to export is only possible in the presence of an excess of unliganded SiaP.

Original languageEnglish
Pages (from-to)1778-1783
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number6
DOIs
Publication statusPublished - 10 Feb 2009

Keywords

  • sialic acid
  • SiaPQM
  • tripartite ATP-independent periplasmic transporter
  • Haemophilus influenzae
  • receptor-dependent translocation
  • EXTRACYTOPLASMIC-SOLUTE-RECEPTOR
  • HAEMOPHILUS-INFLUENZAE
  • ABC TRANSPORTER
  • SIALIC-ACID
  • LACTOCOCCUS-LACTIS
  • CRYSTAL-STRUCTURES
  • MEMBRANE-PROTEINS
  • ESCHERICHIA-COLI
  • VIRULENCE FACTOR
  • EXPRESSION

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