Rescue by vitamin B12 of Escherichia coli cells treated with colicins A and E allows measurement of the kinetics of colicin binding on BtuB

Cavard, D

doi:10.1016/0378-1097(94)90104-x

Cited by 4 publications

(5 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, colicin M is able to block albomycin activity, an antibiotic which also uses FhuA as a receptor [22] , [25] , [26] . Similarly vitamin B 12 , the substrate of the BtuB receptor, is able to inhibit cytotoxicity of the E group colicins which also bind this receptor [27] .…”

Section: Discussionmentioning

confidence: 99%

Ferredoxin Containing Bacteriocins Suggest a Novel Mechanism of Iron Uptake in Pectobacterium spp

2012

View full text Add to dashboard Cite

In order to kill competing strains of the same or closely related bacterial species, many bacteria produce potent narrow-spectrum protein antibiotics known as bacteriocins. Two sequenced strains of the phytopathogenic bacterium Pectobacterium carotovorum carry genes encoding putative bacteriocins which have seemingly evolved through a recombination event to encode proteins containing an N-terminal domain with extensive similarity to a [2Fe-2S] plant ferredoxin and a C-terminal colicin M-like catalytic domain. In this work, we show that these genes encode active bacteriocins, pectocin M1 and M2, which target strains of Pectobacterium carotovorum and Pectobacterium atrosepticum with increased potency under iron limiting conditions. The activity of pectocin M1 and M2 can be inhibited by the addition of spinach ferredoxin, indicating that the ferredoxin domain of these proteins acts as a receptor binding domain. This effect is not observed with the mammalian ferredoxin protein adrenodoxin, indicating that Pectobacterium spp. carries a specific receptor for plant ferredoxins and that these plant pathogens may acquire iron from the host through the uptake of ferredoxin. In further support of this hypothesis we show that the growth of strains of Pectobacterium carotovorum and atrosepticum that are not sensitive to the cytotoxic effects of pectocin M1 is enhanced in the presence of pectocin M1 and M2 under iron limiting conditions. A similar growth enhancement under iron limiting conditions is observed with spinach ferrodoxin, but not with adrenodoxin. Our data indicate that pectocin M1 and M2 have evolved to parasitise an existing iron uptake pathway by using a ferredoxin-containing receptor binding domain as a Trojan horse to gain entry into susceptible cells.

show abstract

Section: Discussionmentioning

confidence: 99%

Ferredoxin Containing Bacteriocins Suggest a Novel Mechanism of Iron Uptake in Pectobacterium spp

2012

View full text Add to dashboard Cite

show abstract

“…For example, the addition of ferric enterobactin to cells expressing FepA protects them from killing by colicin B (672); similar experiments were done using ferrichrome, FhuA, and colicin M (672); cobalamin, BtuB, and E-type colicins (158); or spermine, OmpF, and colicin N (57). However, the nature of competition between colicins and natural metal chelates differs: cobalamin can rescue colicin (A or E)-treated bacteria, suggesting that this metal chelate displaces a bound colicin from BtuB (83). Ferric enterobactin does not displace colicin B on cells, although FepA binds ferric enterobactin with a K d of 24 nM, compared to a K d of 185 nM for colicin B.…”

Section: Competition With the Natural Ligandmentioning

confidence: 97%

Colicin Biology

Cascales

Buchanan

Duché

et al. 2007

Microbiol Mol Biol Rev

970

1,324

View full text Add to dashboard Cite

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.

show abstract

“…1, a and b). Cyanocobalamin (vitamin B 12 , CN-Cbl), a common substrate for BtuB, acts as an inhibitor for E-colicin binding and activity in vivo (10,11). The E-colicins belong to one of the following three cytotoxic classes: (i) membrane depolarizing (or pore forming) colicins such as ColE1; (ii) DNases such as ColE2, ColE7, ColE8, and ColE9; and (iii) RNases such as ColE3, ColE4, ColE5, and ColE6 (7).…”

mentioning

confidence: 99%

Enzymatic E-colicins Bind to Their Target Receptor BtuB by Presentation of a Small Binding Epitope on a Coiled-coil Scaffold

Mohanty

Bishop

et al. 2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Toxins and viruses often initiate their attacks by binding to specific proteins on the surfaces of target cells. Bacterial toxins (e.g. bacteriocins) and viruses (bacteriophages) targeting Gram-negative bacteria typically bind to outer membrane proteins. Bacterial E-colicins target Escherichia coli by binding to the outer membrane cobalamin transporter BtuB. Colicins are tripartite molecules possessing receptor-binding, translocation, and toxin domains connected by long coiled-coil ␣-helices. Surprisingly, the crystal structure of colicin E3 does not possess a recognizable globular fold in its receptor-binding domain. We hypothesized that the binding epitope of enzymatic E-colicins is a short loop connecting the two ␣-helices that comprise the coiledcoil region and that this flanking coiled-coil region serves to present the loop in a binding-capable conformation. To test this hypothesis, we designed and synthesized a 34-residue peptide (E-peptide-1) corresponding to residues Ala 366 -Arg 399 of the helix-loop-helix region of colicin E3. Cysteines placed near the ends of the peptide (I372C and A393C) enabled crosslinking for reduction of conformational entropy and formation of a peptide structure that would present the loop epitope. A fluorescent analog was also made for characterization of binding by measurement of fluorescence polarization. Our analysis shows the following. (i) E-peptide-1 is predominantly random coil in aqueous solution, but disulfide bond formation increases its ␣-helical content in both aqueous buffer and solvents that promote helix formation. (ii) Fluorescein-labeled E-peptide-1 binds to purified BtuB in a calcium-dependent manner with a K d of 43.6 ؎ 4.9 nM or 2370 ؎ 670 nM in the presence or absence of calcium, respectively. (iii) In the presence of calcium, cyanocobalamin (CN-Cbl) displaces E-peptide-1 with a nanomolar inhibition constant (K i ‫؍‬ 78.9 ؎ 5.6 nM). We conclude that the BtuB binding sites for cobalamins and enzymatic E-colicins are overlapping but inequivalent and that the distal loop and (possibly) the short ␣-helical flanking regions are sufficient for high affinity binding.A critical first step for the action of many toxins and viruses is binding to proteins or other molecules at the external surface of the target cell. Examples of this process for eukaryotic targets include bacterial toxins and virulence factors that can bind to integrins or other eukaryotic receptors (1), as well as the human immunodeficiency virus that utilizes chemokine receptors (2) and the CD4 surface glycoprotein (3) as co-receptors. This process also occurs in the microbial world, with bacterial toxins (e.g. bacteriocins) and bacterial viruses (bacteriophages) binding to surface proteins of susceptible bacteria. Colicins are bacteriocins produced by and active against strains of Escherichia coli and closely related bacteria (4 -7). Colicins bind to outer membrane proteins such as porins and transporters for cobalamins, siderophores, and nucleosides (4 -7). E-colicins, a group of nine closely rela...

show abstract

Rescue by vitamin B12 of Escherichia coli cells treated with colicins A and E allows measurement of the kinetics of colicin binding on BtuB

Cited by 4 publications

References 22 publications

Ferredoxin Containing Bacteriocins Suggest a Novel Mechanism of Iron Uptake in Pectobacterium spp

Ferredoxin Containing Bacteriocins Suggest a Novel Mechanism of Iron Uptake in Pectobacterium spp

Colicin Biology

Enzymatic E-colicins Bind to Their Target Receptor BtuB by Presentation of a Small Binding Epitope on a Coiled-coil Scaffold

Contact Info

Product

Resources

About