Chitinase system of antagonistic Bacillus cereus 28-9
Date Issued
2006
Date
2006
Author(s)
Huang, Chien-Jui
DOI
en-US
Abstract
Bacillus cereus 28-9 is a chitinolytic bacterium isolated from rhizosphere of lilies. This bacterium showed antagonistic effect against Botrytis elliptica, the pathogen of lily leaf blight, by detached leaf assays. To investigate the involvement of the chitinolytic activity in
antagonism, two chitinase-encoding genes, chiCH and chiCW, have been cloned. ChiCH consists of a signal peptide followed by a catalytic domain. ChiCW consists of a signal
peptide, a catalytic domain, a fibronectin type III-like domain, and a chitin-binding domain. ChiCH and ChiCW are slightly and effectively inhibitory to conidial germination of B. elliptica, respectively, indicating that ChiCW may contribute to the antagonistic activity of B. cereus 28-9 against B. elliptica. In addition, an ideal method for high-level expression of chitinases in E. coli as glutathione-S-transferase fusion proteins was established in this study.
According to the results of kinetics, hydrolysis products, and binding activities, ChiCW is an endo-chitinase and ChiCH is an exo-chitinase. Finally, the functions of the C-terminal region on ChiCW activity were investigated. Compared with ChiCW, ChiCWΔFC exhibited higher activity at high temperature and pH although both enzymes had the same optimal temperature and pH for enzyme activities. The kinetic properties of ChiCW and ChiCWΔFC indicate that
ChiCW hydrolyzes oligomeric and polymeric substrates more efficiently than ChiCWΔFC. Based on the results, we suggest that B. cereus 28-9 proteolytically modifying ChiCW to ChiCWΔFC could improve efficiency of chitin degradation in different environments.
Subjects
幾丁質水解酵素
臘狀芽胞桿菌
百合灰黴病菌
蛋白質大量表現
Chitinase
Bacillus cereus
Botrytis elliptica
Protein overexpression
Type
other
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