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Deletion analysis of the 51-kilodalton protein of the Bacillus sphaericus 2362 binary mosquitocidal toxin: construction of derivatives equivalent to the larva-processed toxin
Author(s) -
Marta A. Clark,
Paul Baumann
Publication year - 1990
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.172.12.6759-6763.1990
Subject(s) - biology , bacillus sphaericus , biochemistry , amino acid , subtilisin , bacillus subtilis , toxin , microbiology and biotechnology , peptide sequence , n terminus , chymotrypsin , proteolysis , pore forming toxin , trypsin , bacillales , enzyme , bacteria , gene , genetics , microbial toxins
Bacillus sphaericus 2362 produces a binary toxin consisting of 51- and 42-kDa proteins, both of which are required for toxicity to mosquito larvae. Upon ingestion by larvae, these proteins are processed to 43 and 39 kDa, respectively. Using site-directed mutagenesis, we have obtained N- and C-terminal deletions of the 51-kDa protein and expressed them in B. subtilis by using the subtilisin promoter. Removal of 21 amino acids from the N terminus and 53 amino acids from the C terminus resulted in a protein with the same electrophoretic properties as the 43-kDa degradation product which accumulates in the guts of mosquito larvae. This protein was toxic only in the presence of the 42-kDa protein. A deletion of 32 amino acids at the N terminus combined with a 53-amino-acid deletion at the C terminus resulted in a protein which retained toxicity. Toxicity was lost upon a further deletion of amino acids at potential chymotrypsin sites (41 at the N terminus, 61 at the C terminus). Comparison of the processing of the 51- and the 42-kDa proteins indicated that in spite of their sequence similarity proteolysis occurred at different sites.

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