title: Characterization of the pH-mediated solubility of Bacillus thuringiensis var. san diego native delta-endotoxin crystals.
abstract: Native crystals of Bacillus thuringiensis var. san diego, a coleopteran-specific delta-endotoxin, were metabolically labelled with [35S]methionine. Specific activity was 82,000 CPM/micrograms (2.44 Ci/mmol). Using a universal buffer formulated with the same ionic strength at every pH, we determined that native crystals dissolve above pH 10 and below pH 4. At the acidic pH, the rate of solubilization was substantially slower than at the alkaline pH. Recrystallization rates for the toxin were similar regardless of solubilization conditions. The banding patterns in denatured polyacrylamide gel electrophoresis were unaffected by solubilization conditions. Toxicity was higher for soluble toxin compared to crystal toxin, but virtually identical for the acidic and alkaline produced solutions. Acid solubilization is significant because of the acidic midgut of susceptible Coleoptera.
authors.affiliation: Pesticide Research Center, Michigan State University, E. Lansing 48824.
authors.forename: C N
authors.initials: CN
authors.lastname: Koller
authors.forename: L S
authors.initials: LS
authors.lastname: Bauer
authors.forename: R M
authors.initials: RM
authors.lastname: Hollingworth
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D001517:Coleoptera / Q000187:drug effects; D003460:Crystallization; D004064:Digestive System / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D006460:Hemolysin Proteins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011480:Protease Inhibitors / Q000633:toxicity; D012995:Solubility
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D011480:Protease Inhibitors; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D010450:Endopeptidases