The Tol-Pal proteins of the Escherichia coli cell envelope: an energized system required for outer membrane integrity?

Lloubès, Roland; Cascales, Éric; Walburger, Anne; Bouveret, Emmanuelle; Lazdunski, Claude; Bernadac, Alain; Journet, Laure

doi:10.1016/s0923-2508(01)01226-8

Cited by 161 publications

(159 citation statements)

References 45 publications

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“…The Tol-Pal complex of the Escherichia coli cell envelope utilizes the energy of the transmembrane electrochemical gradient of ions or protons to mechanically drive outer membrane stability and probably the late stages of cell division (1,2). The inner membrane TolA protein interacts with outer membraneanchored Pal (peptidoglycan-associated lipoprotein) in a proton-motive force (PMF) 2 -dependent manner (3).…”

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confidence: 99%

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Goemaere

Devert

Lloubès

et al. 2007

Journal of Biological Chemistry

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The TolQRA proteins of Escherichia coli form an inner membrane complex involved in the maintenance of the outer membrane stability and in the late stages of cell division. The TolQR complex uses the proton-motive force to regulate TolA conformation and its interaction with the outer membrane Pal lipoprotein. It has been proposed that an ion channel forms at the TolQR transmembrane helix interface. This complex assembles with a minimal TolQ/TolR ratio of 4:2, therefore involving at least 14 transmembrane helices, which may form the ion pathway. The C-terminal periplasmic domain of TolR protein interacts with TolQ and has been proposed to control the TolQR channel activity. Here, we constructed unique cysteine substitutions in the last 27 residues of TolR. Each of the substitutions results in a functional TolR protein. Disulfide cross-linking demonstrates that the TolQR complex is dynamic, involving conformational modifications of TolR C-terminal domain. We monitored these structural changes by cysteine accessibility experiments and showed that the conformation of this domain is responsive to the proton-motive force and on the presence of critical residues of the ion pathway.

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Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Goemaere

Devert

Lloubès

et al. 2007

Journal of Biological Chemistry

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“…Group A colicins (ColA, E1 to E9) use the Tol system (composed of TolA, -B, -Q, and -R), whereas group B colicins (ColB, -Ia, -Ib, -D, -M, -5, and -10) use the Ton system (TonB, ExbB, and ExbD) (9,10). Both the Ton and Tol systems are coupled to the proton motive force across the inner membrane, acting as energy transducers for active transport (Ton) or maintenance of OM integrity (Tol) (24). Most colicins also required porins for their transport across the OM.…”

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Release of Immunity Protein Requires Functional Endonuclease Colicin Import Machinery

et al. 2006

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Bacteria producing endonuclease colicins are protected against the cytotoxic activity by a small immunity protein that binds with high affinity and specificity to inactivate the endonuclease. This complex is released into the extracellular medium, and the immunity protein is jettisoned upon binding of the complex to susceptible cells. However, it is not known how and at what stage during infection the immunity protein release occurs. Here, we constructed a hybrid immunity protein composed of the enhanced green fluorescent protein (EGFP) fused to the colicin E2 immunity protein (Im2) to enhance its detection. The EGFP-Im2 protein binds the free colicin E2 with a 1:1 stoichiometry and specifically inhibits its DNase activity. The addition of this hybrid complex to susceptible cells reveals that the release of the hybrid immunity protein is a time-dependent process. This process is achieved 20 min after the addition of the complex to the cells. We showed that complex dissociation requires a functional translocon formed by the BtuB protein and one porin (either OmpF or OmpC) and a functional import machinery formed by the Tol proteins. Cell fractionation and protease susceptibility experiments indicate that the immunity protein does not cross the cell envelope during colicin import. These observations suggest that dissociation of the immunity protein occurs at the outer membrane surface and requires full translocation of the colicin E2 N-terminal domain.

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“…The Tol-Pal proteins of the Escherichia coli cell envelope are critical to maintain outer membrane stability (1,2). In many bacteria, including pathogenic strains, mutations within the genes encoding these proteins display a lethal phenotype, suggesting that the Tol-Pal proteins fulfill an essential function in the bacterial cell (1).…”

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confidence: 99%

“…In many bacteria, including pathogenic strains, mutations within the genes encoding these proteins display a lethal phenotype, suggesting that the Tol-Pal proteins fulfill an essential function in the bacterial cell (1). Several observations suggested an important function of the Tol-Pal proteins in cell division or outer membrane biogenesis and stability.…”

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confidence: 99%

“…Recently, Yeh et al (5) showed that the Tol-Pal proteins of C. crescentus regulate the localization of the TipN polar factor and are therefore key components of the cell envelope structure and of polar development. Finally, tol-pal mutant cells have been shown to release outer membrane vesicles and present important outer membrane defects such as increased susceptibility to toxic compounds and leakage of periplasmic content (1,6).…”

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confidence: 99%

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Mapping the Interactions between Escherichia coli TolQ Transmembrane Segments

Zhang

Goemaere

Seddiki

et al. 2011

Journal of Biological Chemistry

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The Tol-Pal proteins of the Escherichia coli cell envelope: an energized system required for outer membrane integrity?

Cited by 161 publications

References 45 publications

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Movements of the TolR C-terminal Domain Depend on TolQR Ionizable Key Residues and Regulate Activity of the Tol Complex

Release of Immunity Protein Requires Functional Endonuclease Colicin Import Machinery

Mapping the Interactions between Escherichia coli TolQ Transmembrane Segments

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