TonB-dependent receptors - Structural perspectives

Andrew D. Ferguson, Johann Deisenhofer

Research output: Contribution to journalReview articlepeer-review

122 Scopus citations


Plants, bacteria, fungi, and yeast utilize organic iron chelators (siderophores) to establish commensal and pathogenic relationships with hosts and to survive as free-living organisms. In Gram-negative bacteria, transport of siderophores into the periplasm is mediated by TonB-dependent receptors. A complex of three membrane-spanning proteins TonB, ExbB and ExbD couples the chemiosmotic potential of the cytoplasmic membrane with siderophore uptake across the outer membrane. The crystallographic structures of two TonB-dependent receptors (FhuA and FepA) have recently been determined. These outer membrane transporters show a novel fold consisting of two domains. A 22-stranded antiparallel β-barrel traverses the outer membrane and adjacent β-strands are connected by extracellular loops and periplasmic turns. Located inside the β-barrel is the plug domain, composed primarily of a mixed four-stranded β-sheet and a series of interspersed α-helices. Siderophore binding induces distinct local and allosteric transitions that establish the structural basis of signal transduction across the outer membrane and suggest a transport mechanism.

Original languageEnglish (US)
Pages (from-to)318-332
Number of pages15
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number2
StatePublished - Oct 11 2002


  • Outer membrane protein
  • Siderophore
  • Signal transduction
  • TonB-dependent receptor
  • Transporter

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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