Regulation of expression of the Lactobacillus pentosus xylAB operon
Regulation of expression of the Lactobacillus pentosus xylAB operon
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DOI：
10.1128/jb.179.17.5391-5397.1997
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发表时间：
1997-09-01
影响因子：
3.2
通讯作者：
Pouwels, PH
中科院分区：
文献类型：
--
作者：
Lokman, BC;Heerikhuisen, M;Pouwels, PH
戊糖乳杆菌的木糖簇由五个基因组成，其中两个基因xylAB形成操纵子并编码参与木糖分解的酶，而第三个基因编码调节蛋白XyIR。通过引入携带xyl操纵基因的多拷贝质粒和破坏染色体xylR基因，表明L.戊糖xylR编码阻遏物。xylR突变体中xylAB的组成型表达被葡萄糖阻遏，表明葡萄糖阻遏不需要XylR。与野生型细菌相比，当细菌从葡萄糖转移到木糖培养基时，xylR突变体显示出延长的滞后期。不同生长阶段在木糖培养基中生长速率的差异与L. pentosus野生型或xylR突变体细菌，但在干酪乳杆菌中与含有xglAB的质粒正相关。用ccpA突变体进一步研究葡萄糖阻遏。克隆了L.通过PCR分离戊糖并用于构建ccpA敲除突变体。L. pentosus xylA表明CcpA参与葡萄糖的表达。CcpA也被证明参与嗜淀粉乳杆菌的cw-淀粉酶启动子的葡萄糖阻遏，这是通过证明在α-淀粉酶启动子控制下的氯霉素乙酰转移酶基因的葡萄糖阻遏在嗜淀粉乳杆菌中被强烈降低。戊糖菌ccpA突变株。
The xylose cluster of Lactobacillus pentosus consists of five genes, two of which, xylAB, form an operon and code for the enzymes involved in the catabolism of xylose while a third encodes a regulatory protein, XyIR. By introduction of a multicopy plasmid carrying the xyl operator and by disruption of the chromosomal xylR gene, it was shown that L. pentosus xylR encodes a repressor. Constitutive expression of xylAB in the xylR mutant is repressed by glucose, indicating that glucose repression does not require XylR. The xylR mutant displayed a prolonged lag phase compared to wild-type bacteria when bacteria were shifted from glucose to xylose medium. Differences in the growth rate in xylose medium at different stages of growth are not correlated with differences in levels of xylAB transcription in L. pentosus wild-type or xylR mutant bacteria but are positively correlated in Lactobacillus casei with a plasmid containing xglAB. Glucose repression was further investigated with a ccpA mutant. An 875-bp internal fragment of the ccpA gene of L. pentosus was isolated by PCR and used to construct a ccpA knockout mutant. Transcription analysis of L. pentosus xylA Showed that CcpA is involved in glucose expression. CcpA was also shown to be involved in glucose repression of the cw-amylase promoter of Lactobacillus amylovorus by demonstrating that glucose repression of the chloramphenicol acetyltransferase gene under control bf the alpha-amylase promoter is strongly reduced in the L. pentosus ccpA mutant strain.