Siderophores have been studied in great detail over the last 20 years, and although our knowledge of these special iron carriers is vast, new insights and new twists to this well-told story are regularly appearing. In this issue of Journal of Bacteriology, Voulhoux et al. (15) describe the effect of the twinarginine translocation (Tat) system on the biosynthesis and the uptake of siderophores b...

Selected aminothiazolyl-oxime cephalosporin congeners substituted at C-3' with a catechol moiety were used to probe the basis of the enhanced antibacterial activity against Escherichia coli K-12 often associated with chemical modifications of this type. Evidence is presented for a tonB-dependent illicit transport of the compounds across the outer membrane of E. coli K-12, the process involving ...

Iron is an essential nutrient for most living organisms. To acquire iron from their environment, Gram-negative bacteria use TonB-dependent transporters that bind host proteins at the bacterial surface and transport iron or heme to the periplasm via the Ton machinery. TonB-dependent transporters are barrel-shaped outer membrane proteins with 22 transmembrane domains, 11 surface-exposed loops, an...

Neisseria gonorrhoeae ordinarily requires both HpuA and HpuB to use hemoglobin (Hb) as a source of iron for growth. Deletion of HpuA resulted in reduced Hb binding and failure of growth on Hb. We identified rare Hb-utilizing colonies (Hb(+)) from an hpuA deletion mutant of FA1090, which fell into two phenotypic classes. One class of the Hb(+) revertants required expression of both TonB and HpuB...

BACKGROUND FhuA, an integral membrane protein of Escherichia coli, actively transports ferrichrome and the structurally related antibiotic albomycin across the outer membrane. The transport is coupled to the proton motive force, which energizes FhuA through the inner-membrane protein TonB. FhuA also transports the semisynthetic rifamycin derivative CGP 4832, although the chemical structure of t...

We present the sequence of a 3500-bp region of the Escherichia coli strain K12 chromosome lying between the tryptophan operon and the tonB gene. Analysis of the sequence yields six open reading frames that have properties characteristic of genes for proteins. The reading frames are closely spaced, and putative transcription units and control sites compose over 95% of the DNA. The sequences of s...

TonB is known to be a bacterial periplasmic protein that transduces proton from the inner membrane to the outer membrane receptor in complex with the ExbB and ExbD proteins. Actinobacillus pleuropneumoniae TonB2 protein is the second TonB protein that is important for iron acquisition and virulence. The TonB2 protein was verified to be immunogenic and could afford partial protection for animals...