Biochemical characterization of Bacillus thuringiensis cytolytic delta-endotoxins

• Published in: Microbiology (Society for General Microbiology) 1994-08, Vol.140 (8), p.1869-1880
• Main Authors: Koni, P.A, Ellar, D.J
• Format: Article
• Language: English
• Subjects: Aedes aegypti; Amino Acid Sequence; Animals; Anopheles gambiae; Bacillus thuringiensis; Bacillus thuringiensis - chemistry; Bacillus thuringiensis - physiology; Bacillus thuringiensis subsp. israelensis; bacillus thuringiensis subsp. kyushuensis; Bacterial Proteins - chemistry; Bacterial Proteins - isolation & purification; Bacterial Proteins - toxicity; Bacterial Toxins; Bacteriology; Biological and medical sciences; Biological Assay; Circular Dichroism; Culex pipiens; Culicidae - drug effects; Culicidae - growth & development; cytolysis; endotoxins; Endotoxins - chemistry; Endotoxins - isolation & purification; Endotoxins - toxicity; Fundamental and applied biological sciences. Psychology; genbank/z14147; Genes, Bacterial; Hemolysin Proteins; Hemolysis; Invertebrates; Larva; larvae; Manduca - drug effects; Manduca - growth & development; Manduca sexta; Microbiology; Molecular Sequence Data; Molecular Weight; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Rabbits; Sequence Alignment; Sequence Homology, Amino Acid; toxicity
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-140-8-1869

The entomocidal delta-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 alpha-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 delta-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.