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Appl. Environ. Microbiol., Jun 1997, 2311-2317, Vol 63, No. 6
WP Donovan, Y Tan and AC Slaney
The nprA gene, encoding Bacillus thuringiensis neutral protease A, was
cloned by the use of gene-specific oligonucleotides. The size of neutral
protease A deduced from the nprA sequence was 566 amino acids (60,982 Da).
The cloned nprA gene was partially deleted in vitro, and the deleted
allele, designated nprA3, was used to construct an nprA3 strain (neutral
protease A-deficient strain) of B. thuringiensis. Growth and sporulation of
the nprA3 strain were similar to those of an isogenic nprA+ strain,
although the extracellular proteolytic activity of the nprA3 strain was
significantly less than that of the nprA+ strain. The nprA3 strain produced
insecticidal crystal proteins that were more stable than those of the
isogenic nprA+ strain after solubilization in vitro, and sporulated
cultures of the nprA3 strain contained higher concentrations of full-length
insecticidal crystal proteins than did those of its isogenic counterpart.
The absence of neutral protease A did not affect the insecticidal activity
of a lepidopteran-specific crystal protein of B. thuringiensis. These
results indicate that crystal protein stability and yield may be improved
by deletion of specific proteases from B. thuringiensis.
Copyright © 1997, American Society for Microbiology
Cloning of the nprA gene for neutral protease A of Bacillus thuringiensis and effect of in vivo deletion of nprA on insecticidal crystal protein
Ecogen, Inc., Langhorne, Pennsylvania 19047, USA.
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