Disease relevance of toxB

• The activity of LEE1, LEE4, and LEE5 promoters was not significantly altered in E. coli O157:H7 strains harboring toxB or efa-1' mutations, indicating that the effect on the expression of LEE-encoded secreted proteins occurs at a posttranscriptional level [1].
• The toxB gene of Corynebacterium diphtheriae bacteriophage beta encoding the B fragment of diphtheria toxin was cloned into an inducible expression vector [2].
• The Clostridium difficile toxA and toxB genes, encoding cytotoxic and enterotoxic proteins responsible for antibiotic-associated colitis and pseudomembranous colitis, were shown to be transcribed both from gene-specific promoters and from promoters of upstream genes [3].
• The toxA- and toxB-encoded polypeptides (LT subunits A and B, respectively) were identified by their immunological cross-reactivity with Vibrio cholerae enterotoxin subunit A or B [4].
• We now report the in vitro assembly of holotoxin from native pertussis toxin B oligomer and recombinant S1 subunits, the latter purified and refolded from insoluble inclusion bodies [5].

High impact information on toxB

• This suggests the possibility that the pilus and toxin B subunit contain homologous sequences [6].
• The toxin B subunit that mediates this binding has also been shown to recognize a glycoprotein receptor with different sugar specificity [6].
• A mutant cholera toxin B subunit that binds GM1- ganglioside but lacks immunomodulatory or toxic activity [7].
• Since the toxins and chimera are all closely related in structure and function, the residue at position 4 (an asparagine in cholera toxin B subunit) appears to be in the epitope of the antibody and, by implication, in the GM1 binding site [8].
• We found that a single amino acid residue in RhoA and RhoD defines the substrate specificity for toxin B and lethal toxin [9].

Chemical compound and disease context of toxB

• Immunologic characteristics of a Streptococcus mutans glucosyltransferase B sucrose-binding site peptide-cholera toxin B-subunit chimeric protein [10].
• The ability of hyperantigenic preparations of synthetically produced Escherichia coli heat-stable toxin (ST) to provide an immunogenically more potent vaccine when cross-linked by the glutaraldehyde reaction to the heat-labile toxin B subunit was assessed [11].
• We compared the adjuvants monophosphoryl lipid A (MPL)/trehalose dicorynomycolate (TDM), cholera toxin B subunit (CTB) and Escherichia coli heat-labile enterotoxin LT(R192G) for their ability to induce a humoral and cellular immune reaction, using fibrillar Abeta1-40/42 as a common immunogen in wildtype B6D2F1 mice [12].

Biological context of toxB

• Introduction of a mini-pO157 plasmid (pIC37) composed of the toxB and ori regions restored full adherence capacity to O157Cu, including production and secretion of the proteins [13].
• toxB gene on pO157 of enterohemorrhagic Escherichia coli O157:H7 is required for full epithelial cell adherence phenotype [13].
• E. coli O157:H7 strains lack efa-1 but encode a homolog on the pO157 plasmid (toxB/l7095) and contain a truncated version of the efa-1 gene (efa-1'/z4332 in O island 122 of the EDL933 chromosome) [1].
• Therefore we searched for corresponding similarities at the DNA level and found, by oligodeoxynucleotide hybridization, C. jejuni chromosomal nucleotide sequences similar to the coding region for a postulated ganglioside GM1-binding site on toxB and eltB [14].
• The virulence plasmid of Escherichia coli O157 strain EDL933 carries a 10-kb putative virulence gene designated toxB [15].

Anatomical context of toxB

• Mutation of toxB and a truncated version of the efa-1 gene in Escherichia coli O157:H7 influences the expression and secretion of locus of enterocyte effacement-encoded proteins but not intestinal colonization in calves or sheep [1].
• Here we report that E. coli O157:H7 toxB and efa-1' single and double mutants exhibit reduced adherence to cultured epithelial cells and show reduced expression and secretion of proteins encoded by the locus of enterocyte effacement (LEE), which plays a key role in the host-cell interactions of EHEC [1].
• Distinct effects of recombinant cholera toxin B subunit and holotoxin on different stages of class II MHC antigen processing and presentation by macrophages [16].
• Whereas toxin B decreased the transepithelial resistance of Caco-2 cells by about 80% after 4 h, CNF1 reduced it by about 40% [17].
• Membranes from unlabeled or [3H]galactose-labeled cells were incubated with toxin B subunits and extracted with Triton X-100, and the solubilized toxin B-receptor complexes were immunoabsorbed with anti-B bound to protein A-Sepharose [18].

Associations of toxB with chemical compounds

• Accordingly, the potential of the double mutant of toxin B to hydrolyze UDP-N-acetylglucosamine was higher than that for UDP-glucose [19].
• The changing of Ile-383 and Gln-385 in toxin B to serine and alanine, respectively, largely increased the acceptance of UDP-N-acetylglucosamine as a sugar donor for modification of RhoA [19].
• Strikingly, blockage of acetylcholine release by lethal toxin and toxin B could be completely removed in <1 s by high frequency stimulation of nerve terminals [20].
• Accordingly, change of the equivalently positioned phenylalanine 85 in RhoD with serine allowed glucosylation by toxin B [9].
• Highly ordered two-dimensional crystals of cholera toxin B-subunit pentamers have been grown by specific interaction with planar lipid films containing monosialoganglioside GM1 [21].

Other interactions of toxB

• Major differences between the plasmids are the absence of katP, espP, and toxB in pSFO157 and, instead of these, the presence of the sfp fimbriae gene cluster and a large part of an F-plasmid transfer region, the latter accounting for most of the additional DNA [22].
• After the well-documented glycolipid GM1 receptor was blocked with the cholera toxin B subunit, LT still activated the second messenger cascade, measured in terms of heightened cellular adenylate cyclase activity, and caused fluid to be secreted into ligated intestinal loops [23].

Analytical, diagnostic and therapeutic context of toxB

• We developed PCR and hybridization tools for the detection of the entire toxB sequence and investigated its presence in a collection of EHEC O157 strains and other EHEC and EPEC strains belonging to different serogroups and isolated from different sources [15].
• Southern blotting analysis showed that toxB sequences were located on large plasmids in EHEC and EPEC O26 as well [15].
• Selective extracellular release of cholera toxin B subunit by Escherichia coli: dissection of Neisseria Iga beta-mediated outer membrane transport [24].
• Based on the crystal structure of C. difficile toxin B, we studied the sugar donor specificity of the toxins by site-directed mutagenesis [19].
• A 9 A two-dimensional projected structure of cholera toxin B-subunit-GM1 complexes determined by electron crystallography [21].

References