The TolB protein interacts with the porins of Escherichia coli

Rigal, Alain; Bouveret, Emmanuelle; Lloubès, Roland; Lazdunski, Claude; Bénédetti, Hélène

doi:10.1128/jb.179.23.7274-7279.1997

Cited by 59 publications

(76 citation statements)

References 26 publications

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“…This requirement for native disorder is undoubtedly a consequence of the colicin cellular uptake mechanism because the narrow lumen of an OmpF monomer is thought to be the entry point for the unfolded polypeptide into the periplasm before translocation across the OM (19). Thereafter, association with TolB would be expedited because OmpF is known to be closely associated with Tol proteins (34). The role of native disorder in colicin translocation is further illustrated by the pore-forming colicin N, which uses OmpF both as a receptor and translocator to the periplasm where the toxin binds TolA.…”

Section: Resultsmentioning

confidence: 99%

Competitive recruitment of the periplasmic translocation portal TolB by a natively disordered domain of colicin E9

Loftus

Walker

Mate

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

155

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The natively disordered N-terminal 83-aa translocation (T) domain of E group nuclease colicins recruits OmpF to a colicin-receptor complex in the outer membrane (OM) as well as TolB in the periplasm of Escherichia coli, the latter triggering translocation of the toxin across the OM. We have identified the 16-residue TolB binding epitope in the natively disordered T-domain of the nuclease colicin E9 (ColE9) and solved the crystal structure of the complex. ColE9 folds into a distorted hairpin within a canyon of the six-bladed ␤-propeller of TolB, using two tryptophans to bolt the toxin to the canyon floor and numerous intramolecular hydrogen bonds to stabilize the bound conformation. This mode of binding enables colicin side chains to hydrogen-bond TolB residues in and around the channel that runs through the ␤-propeller and that constitutes the binding site of peptidoglycan-associated lipoprotein (Pal). Pal is a globular binding partner of TolB, and their association is known to be important for OM integrity. The structure is therefore consistent with translocation models wherein the colicin disrupts the TolB-Pal complex causing local instability of the OM as a prelude to toxin import. Intriguingly, Ca 2؉ ions, which bind within the ␤-propeller channel and switch the surface electrostatics from negative to positive, are needed for the negatively charged T-domain to bind TolB with an affinity equivalent to that of Pal and competitively displace it. Our study demonstrates that natively disordered proteins can compete with globular proteins for binding to folded scaffolds but that this can require cofactors such as metal ions to offset unfavorable interactions.native disorder ͉ thermodynamics ͉ toxin

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Section: Resultsmentioning

confidence: 99%

Competitive recruitment of the periplasmic translocation portal TolB by a natively disordered domain of colicin E9

Loftus

Walker

Mate

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

155

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“…Because the exact function is not known, current research focuses on the link between Tol-Pal proteins and porins, lipopolysaccharides (LPS), or O-antigen biogenesis. It has been shown that the central domain of the TolA protein, as well as the TolB protein, interacts in vitro with major OM trimeric porins such as OmpF, OmpC, LamB, and PhoE in the presence of sodium dodecyl sulfate (150,554). TolA and TolB do not interact with OmpA or the OM denaturated porins.…”

Section: Tol-dependent Colicinsmentioning

confidence: 99%

Colicin Biology

Cascales

Buchanan

Duché

et al. 2007

Microbiol Mol Biol Rev

985

1,324

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SUMMARY Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.

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“…That is the case for the Braun's (murein) lipoprotein (Lpp) ; the peptidoglycan-associated lipoprotein (PAL) (Lazzaroni & Portalier, 1992) ; the periplasmic protein TolB ; and the inner-membrane complex formed by TolQ, TolR and TolA proteins (Lazzaroni et al, 1999). A series of studies have provided evidence for the existence of large complexes containing these proteins that establish a physical link between the inner and the outer membrane (Bouveret et al, 1995(Bouveret et al, , 1999Rigal et al, 1997 ;Clavel et al, 1998 ;Lazzaroni et al, 1999). This function is essential for providing stability and integrity to the cell envelope.…”

Section: Abbreviationsmentioning

confidence: 99%