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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,
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
tolQ,
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
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
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.

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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