Functional screening for aromatic ring oxygenases of an oil contaminated soil metagenome identified 25 different clones bearing monooxygenases coding genes. One fosmid bore an operon containing four tightly linked genes coding for a complete dibenzothiophene biodesulfurization pathway, which included the predicted monooxygenases DszC and DszA, the desulfinase DszB, and an FMN-oxidoreductase designated DszE. The dszEABC operon provided Escherichia coli with the ability to use dibenzothiophene as the only sulfur source. Transcription of the operon is driven from a σN -dependent promoter and regulated by an activator that was designated dszR. DszR has been purified and characterized in vitro and shown to be a constitutively active σN -dependent activator of the group IV, which binds to two contiguous sequences located upstream of the promoter. The dsz promoter and dszE and dszR genes have apparently been recruited from an aliphatic sulfonate biodegradation pathway. If transcribed from a heterologous upstream promoter, the σN -dependent promoter region functions as an 'insulator' that prevents translation of dszE, by binding with its ribosome binding site. Translational coupling, in turn, prevents translation of the downstream dszABC genes. The silencer combined with translational coupling thus represents an effective way of preventing expression of operons when spuriously transcribed from upstream promoters.

中文翻译：

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通过功能宏基因组学鉴定一个完整的二苯并噻吩生物脱硫操纵子及其调节剂。

对油污土壤基因组的芳香环加氧酶进行功能筛选，鉴定出25个带有单加氧酶编码基因的克隆。一个fosmid带有一个操纵子，其操纵子包含四个紧密连接的基因，这些基因编码一个完整的二苯并噻吩生物脱硫途径，包括预测的单加氧酶DszC和DszA，脱硫酶DszB和称为DszE的FMN氧化还原酶。dszEABC操纵子为大肠杆菌提供了使用二苯并噻吩作为唯一硫源的能力。操纵子的转录由依赖于σN的启动子驱动，并由称为dszR的激活剂调控。DszR已在体外进行纯化和表征，显示为IV组的组成型活性σN依赖性激活剂，可与位于启动子上游的两个连续序列结合。显然已经从脂族磺酸盐生物降解途径募集了dsz启动子以及dszE和dszR基因。如果从异源上游启动子转录，则依赖于σN的启动子区域起“绝缘子”的作用，通过与其核糖体结合位点结合来阻止dszE的翻译。反过来，翻译偶联阻止下游dszABC基因的翻译。因此，沉默子与翻译偶联结合是一种防止从上游启动子进行假转录时操纵子表达的有效方法。通过与其核糖体结合位点结合。反过来，翻译偶联阻止下游dszABC基因的翻译。因此，沉默子与翻译偶联结合代表了一种防止操纵子在从上游启动子虚假转录时表达的有效方法。通过与其核糖体结合位点结合。反过来，翻译偶联阻止下游dszABC基因的翻译。因此，沉默子与翻译偶联结合是一种防止从上游启动子进行假转录时操纵子表达的有效方法。