Jacob S, Allmansberger R, Gärtner D, Hillen W
Institut für Mikrobiologie und Biochemie, Friedrich-Alexander Universität Erlangen-Nürnberg, Federal Republic of Germany.
Mol Gen Genet. 1991 Oct;229(2):189-96. doi: 10.1007/BF00272155.
The Bacillus subtilis xyl operon encoding enzymes for xylose utilization is repressed in the absence of xylose and in the presence of glucose. Transcriptional fusions of spoVG-lacZ to this operon show regulation of beta-galactosidase expression by glucose, indicating that glucose repression operates at the level of transcription. A similar result is obtained when glucose is replaced by glycerol, thus defining a general catabolite repression mechanism. A deletion of xylR, which encodes the xylose-sensitive repressor of the operon, does not affect glucose repression. The cis element mediating glucose repression was identified by Bal31 deletion analysis. It is confined to a 34 bp segment located at position +125 downstream of the xyl promoter in the coding sequence for xylose isomerase. Cloning of this segment in the opposite orientation leads to reduced catabolite repression. The homology of this element to various proposed consensus sequences for catabolite repression in B. subtilis is discussed.
编码利用木糖所需酶的枯草芽孢杆菌木糖操纵子，在缺乏木糖且存在葡萄糖的情况下会受到抑制。spoVG - lacZ与该操纵子的转录融合显示，β - 半乳糖苷酶的表达受葡萄糖调控，这表明葡萄糖阻遏作用发生在转录水平。当葡萄糖被甘油替代时，也会得到类似结果，从而确定了一种普遍的分解代谢物阻遏机制。编码该操纵子木糖敏感阻遏物的xylR缺失，并不影响葡萄糖阻遏作用。通过Bal31缺失分析鉴定出了介导葡萄糖阻遏的顺式元件。它局限于位于木糖异构酶编码序列中木糖启动子下游 +125 位置的一个34 bp片段。以相反方向克隆该片段会导致分解代谢物阻遏作用减弱。本文讨论了该元件与枯草芽孢杆菌中各种提出的分解代谢物阻遏共有序列的同源性。
