Refined Structure of Escherichia coli Heat-labile Enterotoxin, a Close Relative of Cholera Toxin

Sixma, Titia K.; Kalk, K.H.; Vanzanten, Bam; Dauter, Zbigniew; Kingma, Jaap; Hol, W.G.J.

doi:10.1006/jmbi.1993.1209

Cited by 280 publications

(269 citation statements)

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“…bundles of cholera toxin and enterotoxin (Sixma et al, 1993a(Sixma et al, , 1993bMerritt et al, 1994). The helices bend at their midpoint, concordant with the occurrence of conserved prolines at positions 10 and 15, thereby widening the pore.…”

Section: Comparison Of the Channei Properties Of The Botxatm Peptide mentioning

confidence: 56%

Formation of ion channels in lipid bilayers by a peptide with the predicted transmembrane sequence of botulinum neurotoxin A

et al. 1995

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Synthetic peptides patterned after the predicted transmembrane sequence of botulinum toxin A were used as tools to identify an ion channel-forming motif. A peptide denoted BoTxATM, with the sequence GAVILLEFIPEIAI PVLGTFALV, forms cation-selective channels when reconstituted in planar lipid bilayers. As predicted, the selfassembled conductive oligomers express heterogeneous single-channel conductances. The most frequent openings exhibit single-channel conductance of 12 and 7 pS in 0.5 M NaCI, and 29 and 9 pS in 0.5 M KC1. In contrast, ion channels are not formed by a peptide of the same amino acid composition as BoTxATM with a scrambled sequence. Conformational energy calculations show that a bundle of four amphipathic a-helices is a plausible structural motif underlying the measured pore properties. These studies suggest that the identified module may play a functional role in the ion channel-forming activity of intact botulinum toxin A.

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Section: Comparison Of the Channei Properties Of The Botxatm Peptide mentioning

confidence: 56%

Formation of ion channels in lipid bilayers by a peptide with the predicted transmembrane sequence of botulinum neurotoxin A

et al. 1995

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“…La toxine CT exerce son activité toxique en se fixant à la surface cellulaire, par l'intermédiaire de ses cinq sous-unités B. Les sousunités B forment une structure pentamé-rique très stable, tel un anneau étroit, avec un trou central, où est reliée la sous-unité A [135,137,138]. La sous-unité A comprend deux composants (A1 et A2) générés par protéolyse et reliés par un pont disulfure.…”

Section: Activation De L'adénylate Cyclaseunclassified

Les récepteurs des entérotoxines bactériennes

Rousset

2000

Vet. Res.

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-Bacterial enterotoxin receptors. Enteric bacterial toxins display a great diversity in their structure, molecular weight and mechanism of action. The interaction of enterotoxins with the intestinal mucosa either leads to a direct effect on the cell membrane or an effect on signal transduction within eukaryotic cells. However, before a toxin can affect a cell, it must after its secretion by a microorganism, recognise and bind to a specific surface molecule, its receptor. Membrane receptors of bacterial enterotoxins have been identified as protein, glycoprotein or glycolipid in nature. The chemical nature of the molecules acting as receptors is crucial and during evolution they have been carefully selected. Some toxins, after their interaction with a receptor molecule, will transduce a signal across the cell membrane while remaining at the cell surface. Other toxins, after this initial binding step with a receptor, will be internalised. Others can form pores leading to leakage of cellular components and cell lysis. Receptors that have been identified often comprise a saccharidic chain that is directly involved in the recognition and binding of the toxin. Today, models explaining toxin-receptor interactions are more complex, including multistep events. This review summarises the knowledge of the interactions between bacterial toxins and membrane receptors present on intestinal mucosa. receptor / intestine / enterotoxin / binding epitope / glycosphingolipidRésumé -Les toxines bactériennes entériques présentent une grande diversité autant dans leur structure que dans leur poids moléculaire et leur mécanisme d'action. L'interaction des entérotoxines avec la muqueuse intestinale conduit soit à un effet direct sur la paroi cellulaire de la cellule hôte, soit à un dérèglement des voies de signalisation de celle-ci. Toutefois, avant même d'affecter la cellule cible, la toxine sécrétée par le micro-organisme devra reconnaître et s'attacher à une molécule présente à la surface cellulaire, son récepteur. Les récepteurs membranaires des entérotoxines bactériennes peuvent être de nature protéique, glycoprotéique ou glycolipidique. La nature chimique de ces récepteurs, sur laquelle repose la spécificité, est primordiale et au cours de l'évolution ceuxci ont été soigneusement sélectionnés. Certaines toxines, une fois en contact avec leur récepteur, envoient un signal à l'intérieur de la cellule tout en demeurant à la surface alors que d'autres toxines sont internalisées. Enfin, certaines toxines bactériennes peuvent former des pores dans la membrane Vet. Res. 31 (2000)

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“…Toxins were diluted in prewarmed Hanks' balanced salt solution (HBSS) containing (per liter): 0.185 g of CaCl 2 , 0.098 g of MgSO 4 , 0.4 g of KCl, 0.06 g of KH 2 PO 4 , 8 g of NaCl, 0.048 g of Na 2 HPO 4 , 1.0 g of glucose, and 10 mM HEPES at pH 7.4, and applied to the apical surface of confluent T84 cell monolayers in Transwell inserts (Costar, Cambridge, MA), followed by incubation at 37°C. Alternatively, T84 cells were placed at 4°C; the toxins diluted in ice-cold HBSS were then applied apically for 30 min at 4°C.…”

Section: Toxin Assaysmentioning

confidence: 99%

“…Both Ctx and Etx are hetero-oligomeric proteins comprised of a single A-subunit (M r 28,000) and five B-subunits (M r 12,000 each) (4 -6). The A-subunit contains two distinct structural domains linked by a disulfide bridge: an A1-fragment (residues ) that displays ADP-ribosyl transferase activity and an A2-fragment (residues 193-240) that mediates interaction with the B-subunit pentamer (4,6). The B-subunits of Ctx and Etx (CtxB and EtxB, respectively) bind to cell surface receptors, principally G M1 -ganglioside, found ubiquitously on the plasma membranes of eukaryotic cells (7).…”

mentioning

confidence: 99%

Structural Basis for the Differential Toxicity of Cholera Toxin and Escherichia coli Heat-labile Enterotoxin

Rodighiero

Aman

Kenny

et al. 1999

Journal of Biological Chemistry

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Cholera toxin (Ctx) and E. coli heat-labile enterotoxin (Etx) are structurally and functionally similar AB 5 toxins with over 80% sequence identity. When their action in polarized human epithelial (T84) cells was monitored by measuring toxin-induced Cl ؊ ion secretion, Ctx was found to be the more potent of the two toxins. Here, we examine the structural basis for this difference in toxicity by engineering a set of mutant and hybrid toxins and testing their activity in T84 cells. This revealed that the differential toxicity of Ctx and Etx was (i) not due to differences in the A-subunit's C-terminal KDEL targeting motif (which is RDEL in Etx), as a KDEL to RDEL substitution had no effect on cholera toxin activity; (ii) not attributable to the enzymatically active A1-fragment, as hybrid toxins in which the A1-fragment in Ctx was substituted for that of Etx (and vice versa) did not alter relative toxicity; and (iii) not due to the B-subunit, as the replacement of the B-subunit in Ctx for that of Etx caused no alteration in toxicity, thus excluding the possibility that the broader receptor specificity of EtxB is responsible for reduced activity. Remarkably, the difference in toxicity could be mapped to a 10-amino acid segment of the A2-fragment that penetrates the central pore of the B-subunit pentamer. A comparison of the in vitro stability of two hybrid toxins, differing only in this 10-amino acid segment, revealed that the Ctx A2-segment conferred a greater stability to the interaction between the A-and B-subunits than the corresponding segment from Etx A2. This suggests that the reason for the relative potency of Ctx compared with Etx stems from the increased ability of the A2-fragment of Ctx to maintain holotoxin stability during uptake and transport into intestinal epithelia.The severe, and at times fatal, diarrheal disease caused by Vibrio cholerae is due to the potent action of cholera toxin (Ctx) 1 (for a review, see Ref. 1). A structurally and functionally similar toxin, heat-labile enterotoxin (Etx), is produced by certain strains of enterotoxigenic Escherichia coli that are responsible for causing the generally milder "traveler's" diarrhea of humans and scouring in farm animals (2, 3). Both Ctx and Etx are hetero-oligomeric proteins comprised of a single A-subunit (M r 28,000) and five B-subunits (M r 12,000 each) (4 -6). The A-subunit contains two distinct structural domains linked by a disulfide bridge: an A1-fragment (residues 1-192) that displays ADP-ribosyl transferase activity and an A2-fragment (residues 193-240) that mediates interaction with the B-subunit pentamer (4, 6). The B-subunits of Ctx and Etx (CtxB and EtxB, respectively) bind to cell surface receptors, principally G M1 -ganglioside, found ubiquitously on the plasma membranes of eukaryotic cells (7). Although Ctx and Etx exhibit a remarkable degree of structural homology, with 81.6% sequence identity between CtxA and EtxA and 82.5% sequence identity between CtxB and EtxB (8 -10), there are a number of subtle physicochemical and function...

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Refined Structure of Escherichia coli Heat-labile Enterotoxin, a Close Relative of Cholera Toxin

Cited by 280 publications

References 0 publications

Formation of ion channels in lipid bilayers by a peptide with the predicted transmembrane sequence of botulinum neurotoxin A

Formation of ion channels in lipid bilayers by a peptide with the predicted transmembrane sequence of botulinum neurotoxin A

Les récepteurs des entérotoxines bactériennes

Structural Basis for the Differential Toxicity of Cholera Toxin and Escherichia coli Heat-labile Enterotoxin

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