Outer membrane active transport: structure of the BtuB:TonB complex

Science. 2006 Jun 2;312(5778):1396-9. doi: 10.1126/science.1127694.


In Gram-negative bacteria, the import of essential micronutrients across the outer membrane requires a transporter, an electrochemical gradient of protons across the inner membrane, and an inner membrane protein complex (ExbB, ExbD, TonB) that couples the proton-motive force to the outer membrane transporter. The inner membrane protein TonB binds directly to a conserved region, called the Ton-box, of the transporter. We solved the structure of the cobalamin transporter BtuB in complex with the C-terminal domain of TonB. In contrast to its conformations in the absence of TonB, the Ton-box forms a beta strand that is recruited to the existing beta sheet of TonB, which is consistent with a mechanical pulling model of transport.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism
  • Biological Transport, Active
  • Crystallography, X-Ray
  • Escherichia coli
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Magnetic Resonance Spectroscopy
  • Membrane Proteins / chemistry*
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / metabolism
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Secondary


  • Bacterial Outer Membrane Proteins
  • BtuB protein, E coli
  • Escherichia coli Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • tonB protein, E coli

Associated data

  • PDB/2GSK