State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
College of Life Sciences, Northeast Agriculture University, Harbin, China.
Microbiol Res. 2020 May;235:126438. doi: 10.1016/j.micres.2020.126438. Epub 2020 Feb 12.
Acetoin (3-hydroxy-2-butanone) is an important physiological metabolic product in many microorganisms. Acetoin breakdown is catalyzed by the acetoin dehydrogenase enzyme system (AoDH ES), which is encoded by acoABCL operon. In this study, we analyzed transcription and regulation of the aco operon in Bacillus thuringiensis (Bt). RT-PCR analysis revealed that acoABCL forms one transcriptional unit. The Sigma 54 controlled consensus sequence was located 12 bp from the acoA transcriptional start site (TSS). β-galactosidase assay revealed that aco operon transcription is induced by acetoin, controlled by sigma 54, and positively regulated by AcoR. The HTH domain of AcoR recognized and specifically bound to a 13-bp inverted repeat region that participates in 30-bp fragment mapping 81 bp upstream of the acoA TSS. The GAF domain in AcoR represses enhancer transcriptional activity at the acoA promoter. Transcriptions of the aco operon and acoR were repressed by glucose via CcpA, and CcpA specifically bound to sequences within the acoR promoter fragment. In the acoABCL and acoR mutants, acetoin use was abolished, suggesting that the aco operon is essential for utilization of acetoin. The data presented here improve our understanding of the regulation of the aco gene cluster in bacteria.
乙酰**（3-羟基-2-丁酮）是许多微生物中重要的生理代谢产物。乙酰分解由乙酰脱氢酶酶系统（AoDH ES）催化，该酶系统由 acoABCL 操纵子编码。在本研究中，我们分析了苏云金芽孢杆菌（Bt）aco 操纵子的转录和调控。RT-PCR 分析表明 acoABCL 形成一个转录单位。Sigma 54 控制的保守序列位于 acoA 转录起始位点（TSS）前 12 个碱基。β-半乳糖苷酶测定表明，aco 操纵子转录受乙酰诱导，受 Sigma 54 控制，由 AcoR 正向调节。AcoR 的 HTH 结构域识别并特异性结合参与 30 个碱基片段的 13 个碱基反向重复区域，该片段位于 acoA TSS 上游 81 个碱基处。AcoR 中的 GAF 结构域抑制 AcoA 启动子增强子的转录活性。aco 操纵子和 acoR 的转录受 CcpA 通过葡萄糖抑制，CcpA 特异性结合 acoR 启动子片段内的序列。在 acoABCL 和 acoR 突变体中，乙酰的利用被废除，这表明 aco 操纵子对于乙酰的利用是必需的。这里呈现的数据提高了我们对细菌 aco 基因簇调控的理解。
