Molecular characterization of the TonB2 protein from the fish pathogen Vibrio anguillarum

Claudia S. López, R. Sean Peacock, Jorge H. Crosa, Hans J. Vogel

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


In the fish pathogen Vibrio anguillarum the TonB2 protein is essential for the uptake of the indigenous siderophore anguibactin. Here we describe deletion mutants and alanine replacements affecting the final six amino acids of TonB2. Deletions of more than two amino acids of the TonB2 C-terminus abolished ferricanguibactin transport, whereas replacement of the last three residues resulted in a protein with wild-type transport properties. We have solved the high-resolution solution structure of the TonB2 C-terminal domain by NMR spectroscopy. The core of this domain (residues 121-206) has an αββαβ structure, whereas residues 76-120 are flexible and extended. This overall folding topology is similar to the Escherichia coli TonB C-terminal domain, albeit with two differences: the β4 strand found at the C-terminus of TonB is absent in TonB2, and loop 3 is extended by 9 Å (0.9 nm) in TonB2. By examining several mutants, we determined that a complete loop 3 is not essential for TonB2 activity. Our results indicate that the β4 strand of E. coli TonB is not required for activity of the TonB system across Gram-negative bacterial species. We have also determined, through NMR chemical-shift-perturbation experiments, that the E. coli TonB binds in vitro to the TonB box from the TonB2-dependent outer membrane transporter FatA; moreover, it can substitute in vivo for TonB2 during ferric-anguibactin transport in V. anguillarum. Unexpectedly, TonB2 did not bind in vitro to the FatA TonBbox region, suggesting that additional factors may be required to promote this interaction. Overall our results indicate that TonB2 is a representative of a different class of TonB proteins.

Original languageEnglish (US)
Pages (from-to)49-59
Number of pages11
JournalBiochemical Journal
Issue number1
StatePublished - Feb 15 2009


  • Iron transport
  • Nuclear magnetic resonance (NMR)
  • Siderophore
  • TonB
  • TonB box
  • Vibrio anguillarum

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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