Chain Cholera toxin

Fig. 12. Tentative model of the signal transduction chain that links the perception of pectic fragments to defense responses in carrot cells. Abbreviations apy, heterotrimeric G protein CaM, calmodulin 4CL, 4-coumarate-CoA ligase CTX, cholera toxin FC, fusicoccine GDP-P-S and GTP-y-S, guanosine 5 -0-(2-thiodiphosphate) and guanosine 5 -0-(3-thiotriphosphate) IP3, 1,4,5-inositol trisphosphate PAL, phenylalanine ammonia-lyase PLC, phospholipase C PR, pathogenesis related PTX, pertussis toxin Rc, receptor SP, staurosporine. Activation and inhibition are symbolized by + and -respectively.

CP coat protein CtxB cholera toxin B subunit scFv single chain Fv antibody fragment TMOF trypsin modulating oostatic factor MAB monoclonal antibody GFP green fluorescent protein CPV Canine parvovirus BHV Bovine herpes virus FMDV Foot and mouth disease virus HCV Hepatitis C virus HRV Human rhino Virus MEV Mink enteritis virus MHV Murine hepatitis virus MV Measles virus RSV Respiratory syncytial virus... 

Caveolae can mediate the delivery of CtxB that binds to GM1 ganglioside at the plasma membrane and is delivered to intracellular compartments. Cholera toxin, produced by Vibrio cholerae, consists of five identical subunits B and one A chain. In addition to labeled SV40 and caveolin-1-GFP, CtxB is one of the most commonly used caveolae markers. However, two groups reported that the toxin is internalized by either a clathrin-independent caveolae pathway or a clathrin-dependent uptake, bringing its selectivity/specificity into question (31,81,118). We controlled the suitability of this marker for COS-7 cells pretreated with CPZ, mpCD, and filipin and as expected, the uptake was not influenced by CPZ treatment but was strongly decreased by the latter two (data not shown). 

Li D, O Leary J, Huang Y, Huner NPA, Jevnikar AM, Ma S. (2006) Expression of cholera toxin B subunit and the B chain of human insulin as a fusion protein in transgenic tobacco plants. Plant Cell Rep 25 417-424. 

Figure 7-5 Stereoscopic view of the B5 pentamer of cholera toxin B. The pentamer, known as choleragenoid, has a central hole of 1.5 nm diameter into which a helix from the A subunit is inserted. As viewed here, the front surface of the pentamer has binding sites for the oligosaccharide chains of ganglioside CM, which serves as the toxin receptor. The back side binds the A subunit. See also Box 11-A. From Zhang et al,31...

This toxin subunit is an enzyme, an ADP-ribo-syltransferase which catalyzes transfer of ADP-ribosyl units from the coenzyme NAD+ to specific arginine side chains to form N-ADP-ribosyl derivatives of various proteins. Of the proteins modified by cholera toxin, the most significant is the guanyl nucleotide regulatory protein Gs of the adenylate cyclase system.C/f/h ADP ribosylation of arginine 201 of the a subunit of protein Gs inhibits the GTP hydrolysis that normally allows the protein to relax to an unactivated form.e The ADP-ribosylated Gs keeps adenylate cyclase activated continuously and... 

Cholera toxin B subunit-biotin labeled (lyophilized powder, biotin content 0.9mol/mol protein), peroxidase-labeled IgG anti-rabbit antibody (HRP-Ab, from goat, protein content 0.8mg/ml, affinity isolated antibody), anti-cholera toxin (from rabbit, protein content 48mg/ml, purified toxin from Vibrio cholerae), biotin monoclonal anti-rabbit IgG -y-chain specific (from mouse, protein content 4.2mg/ml), glucose oxidase-biotinamidocaproyl labeled (GOX-B, from Aspergillus niger, lyophilized powder containing 40-70% protein, 137 U/mg), polyoxyeth-ylene-sorbitan monolaurate (Tween 20), bovine serum albumin (fraction... 

CBl receptor mRNA was detected in the GI tract of the rat, mouse and guinea-pig (Izzo et al. 2003 Storr et al. 2002). In whole gut homogenates from the guinea-pig, CBl receptor and CB2 receptor-like mRNA transcripts were detected, whereas only CBl receptor mRNA was found in the myenteric plexus (Griffin et al. 1997). CBl receptor mRNA was also detected in human colon (Shire et al. 1995). Reverse transcription-polymerase chain reaction (RT-PCR) found both CBi receptor and CB2 receptor mRNA in the rat stomach and mouse small intestine (Izzo et al. 2003 Storr et al. 2002). The expression level of CBi receptor mRNA in the latter was upregulated after treatment with cholera toxin (Izzo et al. 2003). 

Cholera toxin catalyzes the attachment of ADP-ribose to an arginine side chain of the Gso subunit of the guanine nucleotide binding protein in the adenylate... 

In conformity with the sequential processing of bacterial protein toxins such as diphtheria or cholera toxin, the action of BoNT involves multiple discrete steps binding to surface receptors, internalization via receptor-mediated endocytosis, transport from endosome to cytosol, and cleavage of target proteins in the cytosol. " Binding and internalization are mediated by the C- and N-terminal domains of the BoNT H-chain, respectively. The L-chains have zinc metalloprotease activity, targeted selectively to one of three proteins that are required for the docking and fusion of synaptic vesicles with active zones at the cytoplasmic surface of the nerve terminal. 

The interaction of cholera toxin with vesicles is strong enough to permit perturbation in the lipid membrane, but it does not affect the dissociation of the active a-chain from the vesicle-bound toxin. 

Cholera toxin (including the nontoxic B chain, CTB) is a potent immune response adjuvant, and fusion of antigens to CTB enhances the binding and effectiveness of antigens. An insulin-CTB fusion protein produced from bacteria has proved difficult to purify, however potato-based expression of such a fusion protein has been successful and oral administration shown to reduce inflammation of the pancreas in diabetic mice [75],... 

Lycke NY. Cholera toxin promotes B-cell isotype switching by two dififerent mechanisms. cAMP induction augments germ-line H-chain RNA transcripts whereas membrane ganglioside GMl-receptor binding enhances later events in differentiation. J Immunol 1993 150(11) 4810-4821. 

A simple radioactive assay has been developed to evaluate the combination of subunits from human chorionic gonadotrophin (hCG), thyrotrophin, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). The method is claimed to detect the formation of less than one picomole of the resulting hormone. An homology in the amino-acid sequences has been detected in the B-chain of cholera toxin and the /S-subunits of thyrotrophin, LH, hCG, and FSH, and is thought to represent the site on these proteins that binds to the receptors on membranes. Hybridization studies using the a- and -subunits of thyrotrophin, lutrophin, and CG from different species e.g. sheep, cattle, and humans) demonstrated increases in the a-helix and -sheet contents of the proteins, comparable to those observed in the thyrotrophin subunit assembly. ... 

Kurosky, A., Market, D. E., Peterson, J. W., and Fitch, W. M., 1977, Primary structure of cholera toxin B-chain A glycoprotein hormone analog Science 195 299. 

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