Holotoxin disassembly by protein disulfide isomerase is less efficient for Escherichia coli heat-labile enterotoxin than cholera toxin. 2022

Albert Serrano, and Jessica L Guyette, and Joel B Heim, and Michael Taylor, and Patrick Cherubin, and Ute Krengel, and Ken Teter, and Suren A Tatulian
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816, USA.

Cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) are structurally similar AB5-type protein toxins. They move from the cell surface to the endoplasmic reticulum where the A1 catalytic subunit is separated from its holotoxin by protein disulfide isomerase (PDI), thus allowing the dissociated A1 subunit to enter the cytosol for a toxic effect. Despite similar mechanisms of toxicity, CT is more potent than LT. The difference has been attributed to a more stable domain assembly for CT as compared to LT, but this explanation has not been directly tested and is arguable as toxin disassembly is an indispensable step in the cellular action of these toxins. We show here that PDI disassembles CT more efficiently than LT, which provides a possible explanation for the greater potency of the former toxin. Furthermore, direct examination of CT and LT domain assemblies found no difference in toxin stability. Using novel analytic geometry approaches, we provide a detailed characterization of the positioning of the A subunit with respect to the B pentamer and demonstrate significant differences in the interdomain architecture of CT and LT. Protein docking analysis further suggests that these global structural differences result in distinct modes of PDI-toxin interactions. Our results highlight previously overlooked structural differences between CT and LT that provide a new model for the PDI-assisted disassembly and differential potency of these toxins.

UI MeSH Term Description Entries
D002772 Cholera Toxin An ENTEROTOXIN from VIBRIO CHOLERAE. It consists of two major protomers, the heavy (H) or A subunit and the B protomer which consists of 5 light (L) or B subunits. The catalytic A subunit is proteolytically cleaved into fragments A1 and A2. The A1 fragment is a MONO(ADP-RIBOSE) TRANSFERASE. The B protomer binds cholera toxin to intestinal epithelial cells and facilitates the uptake of the A1 fragment. The A1 catalyzed transfer of ADP-RIBOSE to the alpha subunits of heterotrimeric G PROTEINS activates the production of CYCLIC AMP. Increased levels of cyclic AMP are thought to modulate release of fluid and electrolytes from intestinal crypt cells. Cholera Toxin A,Cholera Toxin B,Cholera Toxin Protomer A,Cholera Toxin Protomer B,Cholera Toxin Subunit A,Cholera Toxin Subunit B,Choleragen,Choleragenoid,Cholera Enterotoxin CT,Cholera Exotoxin,Cholera Toxin A Subunit,Cholera Toxin B Subunit,Procholeragenoid,Enterotoxin CT, Cholera,Exotoxin, Cholera,Toxin A, Cholera,Toxin B, Cholera,Toxin, Cholera
D004768 Enterotoxins Substances that are toxic to the intestinal tract causing vomiting, diarrhea, etc.; most common enterotoxins are produced by bacteria. Staphylococcal Enterotoxin,Enterotoxin,Staphylococcal Enterotoxins,Enterotoxin, Staphylococcal,Enterotoxins, Staphylococcal
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006027 Glycosides Any compound that contains a constituent sugar, in which the hydroxyl group attached to the first carbon is substituted by an alcoholic, phenolic, or other group. They are named specifically for the sugar contained, such as glucoside (glucose), pentoside (pentose), fructoside (fructose), etc. Upon hydrolysis, a sugar and nonsugar component (aglycone) are formed. (From Dorland, 28th ed; From Miall's Dictionary of Chemistry, 5th ed) Glycoside
D006358 Hot Temperature Presence of warmth or heat or a temperature notably higher than an accustomed norm. Heat,Hot Temperatures,Temperature, Hot,Temperatures, Hot
D014315 Triterpenes A class of terpenes (the general formula C30H48) formed by the condensation of six isoprene units, equivalent to three terpene units. Triterpene,Triterpenoid,Triterpenoids
D055550 Protein Stability The ability of a protein to retain its structural conformation or its activity when subjected to physical or chemical manipulations. Protein Stabilities,Stabilities, Protein,Stability, Protein
D062105 Molecular Docking Simulation A computer simulation technique that is used to model the interaction between two molecules. Typically the docking simulation measures the interactions of a small molecule or ligand with a part of a larger molecule such as a protein. Molecular Docking,Molecular Docking Simulations,Molecular Docking Analysis,Analysis, Molecular Docking,Docking Analysis, Molecular,Docking Simulation, Molecular,Docking, Molecular,Molecular Docking Analyses,Molecular Dockings,Simulation, Molecular Docking
D019704 Protein Disulfide-Isomerases Sulfur-sulfur bond isomerases that catalyze the rearrangement of disulfide bonds within proteins during folding. Specific protein disulfide-isomerase isoenzymes also occur as subunits of PROCOLLAGEN-PROLINE DIOXYGENASE. Protein Disulfide Isomerase,Protein Disulfide-Isomerase,Disulfide Interchange Enzyme,Disulfide Isomerase,Glycosylation Site-Binding Protein,Sulfhydryl-Disulfide Interchange Enzyme,Thiol-Disulfide Transhydrogenase,Trypanothione-Glutathione Thioltransferase,Disulfide Isomerase, Protein,Disulfide-Isomerase, Protein,Disulfide-Isomerases, Protein,Enzyme, Disulfide Interchange,Enzyme, Sulfhydryl-Disulfide Interchange,Glycosylation Site Binding Protein,Interchange Enzyme, Disulfide,Interchange Enzyme, Sulfhydryl-Disulfide,Isomerase, Disulfide,Isomerase, Protein Disulfide,Protein Disulfide Isomerases,Protein, Glycosylation Site-Binding,Site-Binding Protein, Glycosylation,Sulfhydryl Disulfide Interchange Enzyme,Thiol Disulfide Transhydrogenase,Thioltransferase, Trypanothione-Glutathione,Transhydrogenase, Thiol-Disulfide,Trypanothione Glutathione Thioltransferase
D020134 Catalytic Domain The region of an enzyme that interacts with its substrate to cause the enzymatic reaction. Active Site,Catalytic Core,Catalytic Region,Catalytic Site,Catalytic Subunit,Reactive Site,Active Sites,Catalytic Cores,Catalytic Domains,Catalytic Regions,Catalytic Sites,Catalytic Subunits,Core, Catalytic,Cores, Catalytic,Domain, Catalytic,Domains, Catalytic,Reactive Sites,Region, Catalytic,Regions, Catalytic,Site, Active,Site, Catalytic,Site, Reactive,Sites, Active,Sites, Catalytic,Sites, Reactive,Subunit, Catalytic,Subunits, Catalytic

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