Skip to main content
Allosteric Signaling Is Bidirectional in an Outer-Membrane Transport Protein
Biophysical Journal
  • Arthur Sikora, University of Virginia
  • Benesh Joseph, University of Frankfurt - Germany
  • Morgan Matson, University of Virginia
  • Jacob R. Staley, University of Virginia
  • David S. Casifo, University of Virginia
Document Type
Publication Date

In BtuB, the Escherichia coli TonB-dependent transporter for vitamin B12, substrate binding to the extracellular surface unfolds a conserved energy coupling motif termed the Ton box into the periplasm. This transmembrane signaling event facilitates an interaction between BtuB and the inner-membrane protein TonB. In this study, continuous-wave and pulse electron paramagnetic resonance in a native outer-membrane preparation demonstrate that signaling also occurs from the periplasmic to the extracellular surface in BtuB. The binding of a TonB fragment to the periplasmic interface alters the configuration of the second extracellular loop and partially dissociates a spin-labeled substrate analog. Moreover, mutants in the periplasmic Ton box that are transport-defective alter the binding site for vitamin B12 in BtuB. This work demonstrates that the Ton box and the extracellular substrate binding site are allosterically coupled in BtuB, and that TonB binding may initiate a partial round of transport.


©2016 Biophysical Society.

Additional Comments
NIH grant #: GM035215; Deutsch Forschungsgemeinschaft grant #: SFB 807
Citation Information
Arthur Sikora, Benesh Joseph, Morgan Matson, Jacob R. Staley, et al.. "Allosteric Signaling Is Bidirectional in an Outer-Membrane Transport Protein" Biophysical Journal Vol. 111 Iss. 9 (2016) p. 1908 - 1918 ISSN: 0006-3495
Available at: