Structure and function of cholera toxin and the related Escherichia coli heat-labile enterotoxin.

Escherichia coli enterotoxin (LT) and the homologous cholera toxin (CT) are A-B toxins that cause travelers' diarrhea and cholera, respectively. So far, experimental live and killed vaccines against these diseases have been developed using only the nontoxic B portion of these toxins. The enzymatically active A subunit has not been used because it is responsible for the toxicity and it is reported to induce a negligible titer of toxin neutralizing antibodies. We used site-directed mutagenesis to inactivate the ADP-ribosyltransferase activity of the A subunit and obtained nontoxic derivatives of LT that elicited a good titer of neutralizing antibodies recognizing the A subunit. These LT mutants and equivalent mutants of CT may be used to improve live and killed vaccines against cholera and enterotoxinogenic E. coli.

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Micro-analysis of pure deoxyribonucleic acid-dependent ribonucleic acid polymerase from Escherichia coli. Action of heparin and rifampicin on structure and function

Biochemical Journal ◽

10.1042/bj1170623 ◽

1970 ◽

Vol 117 (3) ◽

pp. 623-631 ◽

Cited By ~ 35

Author(s):

Volker Neuhoff ◽

Wolf-Bernhard Schill ◽

Hans Sternbach

Keyword(s):

Escherichia Coli ◽

Rna Polymerase ◽

Rna Synthesis ◽

Deoxyribonucleic Acid ◽

Structure And Function ◽

Disc Electrophoresis ◽

Inhibitory Mechanism ◽

And Function ◽

Micro Analysis ◽

Template Complex

By using micro disc electrophoresis and micro-diffusion techniques, the interaction of pure DNA-dependent RNA polymerase (EC 2.7.7.6) from Escherichia coli with the template, the substrates and the inhibitors heparin and rifampicin was investigated. The following findings were obtained: (1) heparin converts the 24S and 18S particles of the polymerase into the 13S form; (2) heparin inhibits RNA synthesis by dissociating the enzyme–template complex; (3) rifampicin does not affect the attachment of heparin to the enzyme; (4) the substrates ATP and UTP are bound by enzyme loaded with rifampicin; (5) rifampicin is bound by an enzyme–template complex to the same extent as by an RNA-synthesizing enzyme–template complex. From this it is concluded that the mechanism of the inhibition of RNA synthesis by rifampicin is radically different from that by heparin. As a working hypothesis to explain the inhibitory mechanism of rifampicin, it is assumed that it becomes very firmly attached to a position close to the synthesizing site and only blocks this when no synthesis is in progress.

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Biochemical and structural characterization of the novel sialic acid-binding site of Escherichia coli heat-labile enterotoxin LT-IIb

Biochemical Journal ◽

10.1042/bcj20160575 ◽

2016 ◽

Vol 473 (21) ◽

pp. 3923-3936 ◽

Cited By ~ 3

Author(s):

Dani Zalem ◽

João P. Ribeiro ◽

Annabelle Varrot ◽

Michael Lebens ◽

Anne Imberty ◽

...

Keyword(s):

Escherichia Coli ◽

Binding Site ◽

Cholera Toxin ◽

Carbohydrate Binding ◽

Type I ◽

Type Ii ◽

E Coli ◽

B Subunit ◽

Heat Labile ◽

B Subunits

The structurally related AB5-type heat-labile enterotoxins of Escherichia coli and Vibrio cholerae are classified into two major types. The type I group includes cholera toxin (CT) and E. coli LT-I, whereas the type II subfamily comprises LT-IIa, LT-IIb and LT-IIc. The carbohydrate-binding specificities of LT-IIa, LT-IIb and LT-IIc are distinctive from those of cholera toxin and E. coli LT-I. Whereas CT and LT-I bind primarily to the GM1 ganglioside, LT-IIa binds to gangliosides GD1a, GD1b and GM1, LT-IIb binds to the GD1a and GT1b gangliosides, and LT-IIc binds to GM1, GM2, GM3 and GD1a. These previous studies of the binding properties of type II B-subunits have been focused on ganglio core chain gangliosides. To further define the carbohydrate binding specificity of LT-IIb B-subunits, we have investigated its binding to a collection of gangliosides and non-acid glycosphingolipids with different core chains. A high-affinity binding of LT-IIb B-subunits to gangliosides with a neolacto core chain, such as Neu5Gcα3- and Neu5Acα3-neolactohexaosylceramide, and Neu5Gcα3- and Neu5Acα3-neolactooctaosylceramide was detected. An LT-IIb-binding ganglioside was isolated from human small intestine and characterized as Neu5Acα3-neolactohexaosylceramide. The crystal structure of the B-subunit of LT-IIb with the pentasaccharide moiety of Neu5Acα3-neolactotetraosylceramide (Neu5Ac-nLT: Neu5Acα3Galβ4GlcNAcβ3Galβ4Glc) was determined providing the first information for a sialic-binding site in this subfamily, with clear differences from that of CT and LT-I.

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Influence of High Pressure on the Dimerization of ToxR, a Protein Involved in Bacterial Signal Transduction

Applied and Environmental Microbiology ◽

10.1128/aem.02028-08 ◽

2008 ◽

Vol 74 (24) ◽

pp. 7821-7823 ◽

Cited By ~ 14

Author(s):

Kai Linke ◽

Nagarajan Periasamy ◽

Matthias Ehrmann ◽

Roland Winter ◽

Rudi F. Vogel

Keyword(s):

Escherichia Coli ◽

Signal Transduction ◽

High Pressure ◽

Structure And Function ◽

Transmembrane Segments ◽

Bacterial Signal Transduction ◽

Reporter Strains ◽

And Function ◽

First Time

ABSTRACT High hydrostatic pressure (HHP) is suggested to influence the structure and function of membranes and/or integrated proteins. We demonstrate for the first time HHP-induced dimer dissociation of membrane proteins in vivo with Vibrio cholerae ToxR variants in Escherichia coli reporter strains carrying ctx::lacZ fusions. Dimerization ceased at 20 to 50 MPa depending on the nature of the transmembrane segments rather than on changes in the ToxR lipid bilayer environment.

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The mannose transporter of Escherichia coli. Structure and function of the IIABMan subunit.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)74222-7 ◽

1993 ◽

Vol 268 (36) ◽

pp. 27094-27099

Author(s):

B Stolz ◽

M Huber ◽

Z Marković-Housley ◽

B Erni

Keyword(s):

Escherichia Coli ◽

Structure And Function ◽

And Function

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Escherichia coli Heat-Labile Enterotoxin B Subunit Is a More Potent Mucosal Adjuvant than Its Closely Related Homologue, the B Subunit of Cholera Toxin

Infection and Immunity ◽

10.1128/iai.69.5.3476-3482.2001 ◽

2001 ◽

Vol 69 (5) ◽

pp. 3476-3482 ◽

Cited By ~ 57

Author(s):

Douglas G. Millar ◽

Timothy R. Hirst ◽

Denis P. Snider

Keyword(s):

Escherichia Coli ◽

Cholera Toxin ◽

Lymphocyte Proliferation ◽

Vaccine Adjuvants ◽

B Subunit ◽

Heat Labile ◽

Antibody Titers ◽

Enterotoxin B ◽

Draining Lymph Nodes ◽

Stimulation Of

ABSTRACT Although cholera toxin (Ctx) and Escherichia coliheat-labile enterotoxin (Etx) are known to be potent mucosal adjuvants, it remains controversial whether the adjuvanticity of the holotoxins extends to their nontoxic, receptor-binding B subunits. Here, we have systematically evaluated the comparative adjuvant properties of highly purified recombinant EtxB and CtxB. EtxB was found to be a more potent adjuvant than CtxB, stimulating responses to hen egg lysozyme when the two were coadministered to mice intranasally, as assessed by enhanced serum and secretory antibody titers as well as by stimulation of lymphocyte proliferation in spleen and draining lymph nodes. These results indicate that, although structurally very similar, EtxB and CtxB have strikingly different immunostimulatory properties and should not be considered equivalent as prospective vaccine adjuvants.

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