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Appl. Environ. Microbiol., 08 1997, 3254-3260, Vol 63, No. 8
H Cheong and SS Gill
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.
Copyright © 1997, American Society for Microbiology
Cloning and characterization of a cytolytic and mosquitocidal delta- endotoxin from Bacillus thuringiensis subsp. jegathesan
Department of Entomology, University of California, Riverside 92521, USA.
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