title: Formation of disulfide bonded dimer of mutated heat-labile enterotoxin in vivo.
abstract: One of the two cysteines in the B subunit of heat-labile enterotoxin has been changed to a serine by site-directed mutagenesis so that the internal disulfide bond cannot form. The mutant protein, like the wild-type protein synthesised in the presence of the reducing agent dithiothreitol, does not form pentamers in the periplasm but binds to available membranes. Binding to membranes is disrupted by chaotropic agents but not by salt. More than half the molecules of mutant protein form disulfide-bonded dimers when exported to the periplasm but no dimer is detected when the protein is exported to the medium by spheroplasts.
authors.affiliation: Department of Biology, University of York, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Hedges
authors.forename: S J
authors.initials: SJ
authors.lastname: Hardy
mesh_terms: D001427:Bacterial Toxins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D002462:Cell Membrane / Q000378:metabolism; D004220:Disulfides; D004229:Dithiothreitol / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004768:Enterotoxins / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D016296:Mutagenesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D013104:Spheroplasts / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D004220:Disulfides; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; C027538:heat-labile enterotoxin, E coli; D004229:Dithiothreitol