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KMID : 0545120010110010131
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Journal of Microbiology and Biotechnology
2001 Volume.11 No. 1 p.131 ~ p.137
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Carbon Catabolite Repression (CCR) of Expression of the XylanaseA Gene of Bacillus stearothermophilus No.236
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Ha, Gyong Sik
Choi, Il Dong/Choi, Yong Jin
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Abstract
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Previous work has identified that only the catabolite responsive element A (creA; previously called cre-2) out of two potential cre sequences (cre-1: nucleotides +160 to +173 and cre-2: +173 to +186), recognized within the coding region of the xylanaseA gene (xynA) of Bacillus stearothermophilus No. 236, was actually involved in the carbon catabolite repression (CCR) of xynA expression in B. subtilis. However, the level of CCR of xynA expression was significantly lower than that for xvnA expression in the original B. stearothermophilus No. 236strain (70-fold repression). Therefore, to search for an additional cre element in the promoter region, the upstream region of the xynA gene was subcloned by chromosome walking, and as a result, another potential cre element (nucleotide -124∼-137; designated creB) was recognized in this region. The cre-like sequence revealed a high homology to the cre consensus sequence. The xylanase activity of B. subtilis MW15 bearing pWPBR14 (containing creA and creB) cultured in a medium containing xylose as the sole carbon source was about 7.7times higher than that observed for the same culture containing glucose. B. subtilis MW 15 bearing pWPBR23 (containing only creA) produced an activity about 2.4times higher. This pattern of CCR was confirmed using derivatives of xynA:: aprA fusion plasmids. Furthermore, a measurement of the amounts of the xynA transcript showed a similar pattern as that for the production of xylanase. In addition, the synthesis of xylanase in B. subtilis QB7115 [a catabolite control protein A (ccpA) mutant strain] carrying pWPBR14 was almost completely relieved from glucose repression. Together, these results lead to a conclusion that the CCR of the expresssion of the xynA gene is mediated by CcpA binding at creA and creB sites in B. subtilis.
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KEYWORD
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