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Nature. 2016 Oct 6;538(7623):60-65. doi: 10.1038/nature19757. Epub 2016 Sep 21.

Structural insight into the role of the Ton complex in energy transduction.

Author information

1
Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255 CNRS/Aix-Marseille Université, Institut de Microbiologie de la Méditerranée, 13402 Marseille Cedex 20, France.
2
National Institute of Diabetes &Digestive &Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
3
Markey Center for Structural Biology, Department of Biological Sciences, and the Purdue Institute for Inflammation, Immunology and Infectious Diseases, Purdue University, West Lafayette, Indiana 47907, USA.
4
Fachbereich Physik, Freie Universität, 14195 Berlin, Germany.
5
Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, 45810 Bochum, Germany.
6
Departamento de Cirugia Experimental, Instituto de Investigacion Hospital La Paz (IdiPAZ), Paseo de la Castellana 261, 28046 Madrid, Spain.

Abstract

In Gram-negative bacteria, outer membrane transporters import nutrients by coupling to an inner membrane protein complex called the Ton complex. The Ton complex consists of TonB, ExbB, and ExbD, and uses the proton motive force at the inner membrane to transduce energy to the outer membrane via TonB. Here, we structurally characterize the Ton complex from Escherichia coli using X-ray crystallography, electron microscopy, double electron-electron resonance (DEER) spectroscopy, and crosslinking. Our results reveal a stoichiometry consisting of a pentamer of ExbB, a dimer of ExbD, and at least one TonB. Electrophysiology studies show that the Ton subcomplex forms pH-sensitive cation-selective channels and provide insight into the mechanism by which it may harness the proton motive force to produce energy.

PMID:
27654919
PMCID:
PMC5161667
DOI:
10.1038/nature19757
[Indexed for MEDLINE]
Free PMC Article

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