EFFECTS ON TOXICITY OF ELIMINATING A CLEAVAGE SITE IN A PREDICTED INTERHELICAL LOOP IN BACILLUS-THURINGIENSIS CRYIVB DELTA-ENDOTOXIN

Citation
C. Angsuthanasombat et al., EFFECTS ON TOXICITY OF ELIMINATING A CLEAVAGE SITE IN A PREDICTED INTERHELICAL LOOP IN BACILLUS-THURINGIENSIS CRYIVB DELTA-ENDOTOXIN, FEMS microbiology letters, 111(2-3), 1993, pp. 255-261
Citations number
22
Categorie Soggetti
Microbiology
Journal title
ISSN journal
03781097
Volume
111
Issue
2-3
Year of publication
1993
Pages
255 - 261
Database
ISI
SICI code
0378-1097(1993)111:2-3<255:EOTOEA>2.0.ZU;2-Z
Abstract
When activated by treatment with mosquito (Aedes aegypti) gut extract, the Bacillus thuringiensis CryIVB delta-endotoxin lysed A. aegypti ce lls in vitro. SDS-PAGE and N-terminal sequence determination showed th at in addition to removal of the C-terminal half of the molecule, the activated toxin had undergone proteolytic cleavage at two internal reg ions producing 47-48-kDa and 16-18-kDa polypeptides. Aligning the CryI VB protein sequence with the crystallographic structure of the CryIIIA toxin suggested that one set of cleavages occurred in a region before the start of the N-terminal helical bundle and the second cleavage si te occurred in a predicted loop between helices 5 and 6 in the bundle at arginine-203. To investigate the suggestion by Li et al. [8] that i nterhelical proteolysis is important in the cytolytic mechanism of the se toxins, arginine-203 was substituted by alanine. The mutated toxin now resisted proteolysis at this position and showed a marked decrease in cytolysis in vitro but an increase in larvicidal activity.