Two highly related insecticidal crystal proteins of Bacillus thuringiensis subsp. kurstaki possess different host range specificities.
Two genes encoding insecticidal crystal proteins from Bacillus thuringiensis subsp. kurstaki HD-1 were cloned and sequenced. Both genes, designated cryB1 and cryB2, encode polypeptides of 633 amino acids having a molecular mass of ca. 71 kilodaltons (kDa). Despite the fact that these two proteins display 87% identity in amino acid sequence, they exhibit different toxin specificities. The cryB1 gene product is toxic to both dipteran (Aedes aegypti) and lepidopteran (Manduca sexta) larvae, whereas the cryB2 gene product is toxic only to the latter. DNA sequence analysis indicates that cryB1 is the distal gene of an operon which is comprised of three open reading frames (designated orf1, orf2, and cryB1). The proteins encoded by cryB1 and orf2 are components of small cuboidal crystals found in several subspecies and strains of B. thuringiensis; it is not known whether the orf1 or cryB2 gene products are present in cuboidal crystals. The protein encoded by orf2 has an electrophoretic mobility corresponding to a molecular mass of ca. 50 kDa, although the gene has a coding capacity for a polypeptide of ca. 29 kDa. Examination of the deduced amino acid sequence for this protein reveals an unusual structure which may account for its aberrant electrophoretic mobility: it contains a 15-amino-acid motif repeated 11 times in tandem. Escherichia coli extracts prepared from cells expressing only orf1 and orf2 are not toxic to either test insect.
Widner
W R
WR
Department of Microbiology, University of Washington, Seattle 98195.
Whiteley
H R
HR
D000330:Aedes / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000494:pharmacology; D001427:Bacterial Toxins; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004731:Endotoxins; D005796:Genes; D005798:Genes, Bacterial; D006460:Hemolysin Proteins; D007814:Larva; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects; D010957:Plasmids; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis