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Biochem Biophys Res Commun. 1991 Sep 16;179(2):933-8.

The toxic moiety of the Bacillus thuringiensis protoxin undergoes a conformational change upon activation.

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Department of Chemistry, University of Ottawa, Ontario, Canada.


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.

[Indexed for MEDLINE]

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