title: The toxic moiety of the Bacillus thuringiensis protoxin undergoes a conformational change upon activation.
abstract: Proteolytic processing of the 133-kDa crystal protein (protoxin) from Bacillus thuringiensis subsp. kurstaki yields a 67-kDa insecticidal toxin. Differential scanning calorimetry was used to investigate whether the toxic moiety in the protoxin molecule has the same conformation as activated toxin. Compared to protoxin, toxin gives rise to a more complex endotherm which extends over a 10 degrees C broader temperature range and contains a component occurring at a substantially higher temperature than any unfolding transition in the protoxin endotherm. It is concluded that the toxic moiety undergoes a conformational change upon activation in which the thermal stability of at least one of its domains is significantly increased.
authors.affiliation: Department of Chemistry, University of Ottawa, Ontario, Canada.
authors.forename: C T
authors.initials: CT
authors.lastname: Choma
authors.forename: W K
authors.initials: WK
authors.lastname: Surewicz
authors.forename: H
authors.initials: H
authors.lastname: Kaplan
mesh_terms: D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry*; D001427:Bacterial Toxins / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D004731:Endotoxins; D006460:Hemolysin Proteins; D011487:Protein Conformation; D013696:Temperature
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis