Cloning and characterization of a cytolytic and mosquitocidal delta-endotoxin from Bacillus thuringiensis subsp. jegathesan.
A cytolytic toxin gene encoding a 30.1-kDa Cyt2Bb1 toxin protein from B. thuringiensis subsp. jegathasan was cloned employing a limited-growth PCR screening method with forward and reverse oligonucleotide primers designed from N-terminal amino acid sequences of native and trypsin-cleaved protein, respectively. The expressed protein showed little cross-reactivity to the antibody raised against the Cyt1Aa protein. Unlike Cyt1Aa and Cyt2Aa expression, there was little or no visible crystal inclusion formation under microscopic observation. The amino acid sequence alignment indicated 31 and 66% identity to Cyt1Aa and Cyt2Aa, respectively. The sequence alignment for five known cytolytic proteins indicated three highly conserved regions, two in the loop regions between alpha-helices and beta-sheets and one in the loop region between beta-sheets 5 and 6. beta-Blocks 4 to 7 are also conserved, not only structurally but also among the amino acids in the hydrophobic faces. Mosquitocidal activity assays indicated that the Cyt2Bb toxin had less toxicity than Cyt1Aa and had about 600-times-lower toxicity than the wild-type whole toxin crystal. However, both the Cyt2Bb and the Cyt1Aa toxin showed comparable levels of hemolytic activity.
Cheong
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Department of Entomology, University of California, Riverside 92521, USA.
Gill
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D000330:Aedes; D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D001413:Bacillus thuringiensis / Q000235:genetics* / Q000472:pathogenicity; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D001427:Bacterial Toxins; D001483:Base Sequence; D001681:Biological Assay; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004731:Endotoxins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism / Q000633:toxicity*; D015870:Gene Expression; D006460:Hemolysin Proteins; D006461:Hemolysis; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D017433:Protein Structure, Secondary; D011817:Rabbits; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D000907:Antibodies, Bacterial; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D017931:DNA Primers; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis