Biochemical characterization of Bacillus thuringiensis cytolytic δ-endotoxins

P. A. Koni, D. J. Ellar

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


The entomocidal δ-endotoxins CytA and CytB produced by Bacillus thuringiensis (Bt) subspecies israelensis and kyushuensis respectively showed a similar level of toxicity to mosquito larvae but were not toxic to the larvae of the lepidopteran Manduca sexta. CytA and CytB are also similar in sequence, predicted secondary structure and α-helical content, the only obvious difference being a C-terminal fifteen residue 'tail' on CytB. Investigations of the function, if any, of the CytB C-terminal 'tail' showed that this δ-endotoxin is highly expressed and forms inclusions in an acrystalliferous Bt mutant without the aid of the 20 kDa 'helper' protein from Bt subspecies israelensis which is essential for CytA inclusion formation. After proteinase K treatment, CytA and CytB were processed to virtually the same points in a sequence alignment and were equally haemolytic in vitro. However, the results suggested that unprocessed CytB differs from unprocessed CytA in that the former is not haemolytic.

Original languageEnglish (US)
Pages (from-to)1869-1880
Number of pages12
Issue number8
StatePublished - 1994
Externally publishedYes


  • Bacillus thuringiensis
  • CytA
  • CytB
  • δ-endotoxins

ASJC Scopus subject areas

  • Microbiology


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