Structure and function of X-Pro dipeptide repeats in the TonB proteins of Salmonella typhimurium and Escherichia coli

J Mol Biol. 1990 Dec 20;216(4):883-95. doi: 10.1016/S0022-2836(99)80008-4.


The TonB protein is required for several outer membrane transport processes in bacteria. A short 33-residue peptide segment of TonB has been studied by 1H and 13C nuclear magnetic resonance spectroscopy. The sequence of this peptide segment contains multiple Glu-Pro and Lys-Pro dipeptide repeats that maintain rigid, elongated structures and flank a short connecting segment that adopts a beta-strand configuration. This TonB peptide is shown to interact specifically with the FhuA protein, the outer membrane receptor for ferrichrome-iron, providing the first direct evidence that the TonB protein interacts with outer membrane receptors. Interaction with the FhuA protein involves the extended structural element containing positively charged Lys-Pro repeats, and suggests a functional role for this segment of the TonB protein. As TonB is anchored in the cytoplasmic membrane the protein must, uniquely, span the periplasm. These data, together with studies described in the accompanying paper, suggest a model by which TonB serves to transduce conformational information over extended distances, from the cytoplasmic membrane to the outer membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Biological Transport
  • Escherichia coli / physiology*
  • Escherichia coli Proteins*
  • Magnetic Resonance Spectroscopy
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Molecular Structure
  • Peptide Fragments / metabolism
  • Protein Binding
  • Protein Conformation
  • Receptors, Virus*
  • Salmonella typhimurium / physiology*
  • Structure-Activity Relationship


  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • FhuA protein, E coli
  • Membrane Proteins
  • Peptide Fragments
  • Receptors, Virus
  • tonB protein, Bacteria
  • tonB protein, E coli