Pacheco-Sánchez Daniel, Molina-Fuentes Águeda, Marín Patricia, Medina-Bellver Javier-I, González-López Óscar, Marqués Silvia
Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Environmental Protection, Granada, Spain.
Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Environmental Protection, Granada, Spain
Appl Environ Microbiol. 2017 Apr 17;83(9). doi: 10.1128/AEM.03042-16. Print 2017 May 1.
The anaerobic resorcinol degradation pathway in is unique in that it uses an oxidative rather than a reductive strategy to overcome the aromatic ring stability in degradation of this compound, in a process that is dependent on nitrate respiration. We show that the pathway is organized in five transcriptional units, three of which are inducible by the presence of the substrate. Three σ-dependent promoters located upstream from the three operons coding for the main pathway enzymes were identified, which shared a similar structure with conserved upstream activating sequences (UASs) located at 103 to 111 bp from the transcription start site. Expression of the pathway is controlled by the bacterial enhancer-binding proteins (bEBPs) RedR1 and RedR2, two homologous regulators that, despite their high sequence identity (97%), have nonredundant functions: RedR2, the master regulator which also controls RedR1 expression, is itself able to promote transcription from two of the promoters, while RedR1 activity is strictly dependent on the presence of RedR2. The two regulators were shown to interact with each other, suggesting that the natural mode of activation is by forming heterodimers, which become active in the presence of the substrate after its metabolization to hydroxybenzoquinone through the pathway enzymes. The model structure of the N-terminal domain of the proteins is composed of tandem GAF and PAS motifs; the possible mechanisms controlling the activity of the regulators are discussed. is a strict anaerobe that is able to use 1,3-dihydroxybenzene as the sole carbon source in a process that is dependent on nitrate respiration. We have shown that expression of the pathway is controlled by two regulators of almost identical sequences: the bEBPs RedR1 and RedR2, which share 97% identity. These regulators control three promoters with similar structure. Despite their sequence identity, the two bEBPs are not redundant and are both required for maximum pathway expression. In fact, the two proteins function as heterodimers and require activation by the pathway intermediate hydroxyhydroquinone. The structure of the domain sensing the activation signal resembles that of regulators that are known to interact with other proteins.
[具体细菌名称]中的厌氧间苯二酚降解途径独具特色，在于它采用氧化而非还原策略来克服该化合物降解过程中芳香环的稳定性，此过程依赖硝酸盐呼吸作用。我们发现该途径由五个转录单元组成，其中三个可被底物诱导。鉴定出位于编码主要途径酶的三个操纵子上游的三个σ依赖性启动子，它们与位于转录起始位点103至111 bp处的保守上游激活序列（UASs）具有相似结构。该途径的表达由细菌增强子结合蛋白（bEBPs）RedR1和RedR2控制，这两个同源调节因子尽管序列同一性很高（97%），但具有非冗余功能：RedR2作为主要调节因子，也控制RedR1的表达，它自身能够促进两个启动子的转录，而RedR1的活性严格依赖于RedR2的存在。已证明这两个调节因子相互作用，表明天然激活模式是通过形成异二聚体，在底物通过途径酶代谢为羟基苯醌后，异二聚体在底物存在时变得活跃。蛋白质N端结构域的模型结构由串联的GAF和PAS基序组成；讨论了控制调节因子活性的可能机制。[具体细菌名称]是一种严格厌氧菌，能够在依赖硝酸盐呼吸作用的过程中使用1,3 - 二羟基苯作为唯一碳源。我们已表明该途径的表达由两个序列几乎相同的调节因子控制：bEBPs RedR1和RedR2，它们具有97%的同一性。这些调节因子控制三个结构相似的启动子。尽管它们序列相同，但这两个bEBPs并非冗余，且都是途径最大表达所必需的。实际上，这两种蛋白质作为异二聚体发挥作用，需要途径中间体羟基对苯二酚的激活。感知激活信号的结构域结构类似于已知与其他蛋白质相互作用的调节因子。
