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Journal of Bacteriology, July 2001, p. 4110-4114, Vol. 183, No. 14
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.14.4110-4114.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Energy-Dependent Conformational Change in the TolA Protein of Escherichia coli Involves Its N-Terminal Domain, TolQ, and TolR

Pierre Germon,dagger Marie-Céline Ray, Anne Vianney, and Jean Claude Lazzaroni*

Unité de Microbiologie et Génétique, ERS2009 (CNRS-INSA-Université Lyon 1), F-69622 Villeurbanne Cedex, France

Received 26 February 2001/Accepted 18 April 2001

TolQ, TolR, and TolA inner membrane proteins of Escherichia coli are involved in maintaining the stability of the outer membrane. They share homology with the ExbB, ExbD, and TonB proteins, respectively. The last is involved in energy transduction between the inner and the outer membrane, and its conformation has been shown to depend on the presence of the proton motive force (PMF), ExbB, and ExbD. Using limited proteolysis experiments, we investigated whether the conformation of TolA was also affected by the PMF. We found that dissipation of the PMF by uncouplers led to the formation of a proteinase K digestion fragment of TolA not seen when uncouplers are omitted. This fragment was also detected in Delta tolQ, Delta tolR, and tolA(H22P) mutants but, in contrast to the parental strain, was also seen in the absence of uncouplers. We repeated those experiments in outer membrane mutants such as lpp, pal, and Delta rfa mutants: the behavior of TolA in lpp mutants was similar to that observed with the parental strain. However, the proteinase K-resistant fragment was never detected in the Delta rfa mutant. Altogether, these results suggest that TolA is able to undergo a PMF-dependent change of conformation. This change requires TolQ, TolR, and a functional TolA N-terminal domain. The potential role of this energy-dependent process in the stability of the outer membrane is discussed.

* Corresponding author. Mailing address: Unité de Microbiologie et Génétique, ERS2009 (CNRS-INSA-Université Lyon 1), Bât. André Lwoff, 10, rue Dubois, F-69622 Villeurbanne Cedex, France. Phone: (33) 472 43 13 67. Fax: (33) 472 43 26 86. E-mail: lazzaroni{at}biomserv.univ-lyon1.fr.

dagger Present address: Station de Pathologie Aviaire et Parasitologie, Centre INRA de Tours, F-37380 Nouzilly, France.

Journal of Bacteriology, July 2001, p. 4110-4114, Vol. 183, No. 14
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.14.4110-4114.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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