Multiple pqqA genes respond differently to environment and one contributes dominantly to pyrroloquinoline quinone synthesis
Multiple pqqA genes respond differently to environment and one contributes dominantly to pyrroloquinoline quinone synthesis
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DOI：
10.1002/jobm.201300037
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发表时间：
2015-03-01
影响因子：
3.1
通讯作者：
Zhang, Weicai
中科院分区：
文献类型：
--
作者：
Ge, Xin;Wang, Wenxi;Zhang, Weicai
吡咯喹啉醌是细菌中仅次于烟酰胺和黄素的第三种氧化还原辅因子，其生物合成途径由pqqA基因编码的前体肽PqqA起始的5个步骤组成。食甲基菌MP688具有五个拷贝的pqqA基因。在此，转录pqqA基因在不同条件下，通过实时定量PCR和半乳糖苷酶报告基因的报告。多个pqqA基因被证明在PQQ合成中起重要作用并且贡献不同。pqqA1，pqqA2和pqqA4被确定为显性转录超过其他基因，相应地，这三个基因中任何一个的缺失都会导致PQQ合成的减少。值得注意的是，pqqA在低pH和有限的氧气环境中上调，并且当细菌从pH 7.0转移到pH 5.5时，可以诱导pqqA2启动子。缺失分析显示pqqA2启动子内存在抑制转录的区域。在截短的pqqA2启动子的控制下，通过pqq基因的过表达来增加PQQ浓度。这一结果不仅暗示了pqqA2基因存在负转录调控因子，而且为通过删除靶结合序列来提高PQQ产量提供了新的途径。
Pyrroloquinoline quinone is the third redox cofactor after nicotinamide and flavin in bacteria, and its biosynthesis pathway comprise five steps initiated from a precursor peptide PqqA coded by pqqA gene. Methylovorus sp. MP688 is equipped with five copies of pqqA genes. Herein, the transcription of pqqA genes under different conditions by real-time quantitative PCR and -galactosidase reporter genes are reported. Multiple pqqA genes were proved to play significant roles and contribute differently in PQQ synthesis. pqqA1, pqqA2, and pqqA4 were determined to be dominantly transcribed over the others, and correspondingly absence of any of the three genes caused a decrease in PQQ synthesis. Notably, pqqA was up-regulated in low pH and limited oxygen environment, and it is pqqA2 promoter that could be induced when bacteria were transferred from pH 7.0 to pH 5.5. Deletion analysis revealed a region within pqqA2 promoter inhibiting transcription. PQQ concentration was increased by overexpression of pqq genes under control of truncated pqqA2 promoter. The results not only imply there exist negative transcriptional regulators for pqqA2 but also provide us a new approach to achieve higher PQQ production by deleting the target binding sequence.