Involvement of ExbB and TonB in transport across the outer membrane of Escherichia coli: phenotypic complementation of exb mutants by overexpressed tonB and physical stabilization of TonB by ExbB.
E Fischer,K Günter,Volkmar Braun +2 more
TLDR
It is concluded that the ExbB and ExbD proteins contribute to the activity of TonB and, like TonB, are involved in receptor-dependent transport processes across the outer membrane.Abstract:
The exb locus in Escherichia coli consists of two genes, termed exbB and exbD. Exb functions are related to TonB function in that most TonB-dependent processes are enhanced by Exb. Like tonB mutants, exb mutants were resistant to colicin M and albomycin but, in contrast to tonB mutants, showed only reduced sensitivity to colicins B and D. Overexpressed tonB on the multicopy vector pACYC177 largely restored the sensitivity of exb mutants to colicins B, D, and M but only marginally increased sensitivity to albomycin. Suppression of the btuB451 mutation in the structural gene for the vitamin B12 outer membrane receptor protein by a mutation in tonB occurred only in an exb+ strain. Degradation of the unstable overproduced TonB protein was prevented by overproduced ExbB protein. The ExbB protein also stabilized the ExbD protein. Pulse-chase experiments with radiolabeled ferrichrome revealed release of ferrichrome from exbB, tonB, and fhuC mutants, showing that ferrichrome had not crossed the cytoplasmic membrane. It is concluded that the ExbB and ExbD proteins contribute to the activity of TonB and, like TonB, are involved in receptor-dependent transport processes across the outer membrane.read more
Citations
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Journal ArticleDOI
Energy-coupled transport and signal transduction through the Gram-negative outer membrane via TonB-ExbB-ExbD-dependent receptor proteins
TL;DR: It is proposed that the TonB--ExbB-- ExbD complex opens--via an energized conformation of theTonB protein--channels in the outer membrane, formed by proteins which serves as highly specific binding sites for the various ferric siderophores and vitamin B12.
Journal ArticleDOI
Touch and go: tying TonB to transport
Kathleen Postle,Robert J. Kadner +1 more
TL;DR: The TonB system of Gram‐negative bacteria appears to exist for the purpose of transducing the protonmotive force energy from the cytoplasmic membrane to the outer membrane, where it is needed for active transport of iron siderophores, vitamin B12 and, in pathogens, iron from host‐binding proteins.
Book ChapterDOI
Mechanisms of iron acquisition from siderophores by microorganisms and plants
TL;DR: Most bacteria, fungi, and some plants respond to Fe stress by the induction of high-affinity Fe transport systems that utilize biosynthetic chelates called siderophores, whereas other microbial species, such as Streptomyces pilosus, use a low specificity, high-Affinity transport system that recognizes more than one siderophile type.
Journal ArticleDOI
TonB and the gram-negative dilemma.
TL;DR: A model that incorporates information about TonB‐dependent energy transduction modulated by ExbB protein, which stabilizes TonB, and possibly by several other proteins including ExbC, ExbD, and TolQ is presented.
Journal ArticleDOI
Iron acquisition and its control in Pseudomonas aeruginosa: many roads lead to Rome.
Keith Poole,Geoffery A McKay +1 more
TL;DR: Despite the plethora of ferric siderophore receptors in P. aeruginosa, its genome sequence reveals a striking lack of obvious periplasmic and cytoplasmic membrane transport components capable of accommodating these molecules.
References
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Journal ArticleDOI
Suppression of the btuB451 mutation by mutations in the tonB gene suggests a direct interaction between TonB and TonB-dependent receptor proteins in the outer membrane of Escherichia coli
TL;DR: The fact that mutations suppressing the btuB451 mutation occurred in the tonB gene suggests that there is a direct interaction between TonB and TonB-dependent receptors in the outer membrane of E. coli.
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