Extra-cytoplasmic function (ECF) σ-factors are widespread in bacteria, linking environmental stimuli with changes in gene expression. These transcription factors span several phylogenetically distinct groups and are remarkably diverse in their activation and regulatory mechanisms. Here, we describe the structural and biochemical features of a Mycobacterium tuberculosis ECF factor σ^J that suggests that the SnoaL_2 domain at the C-terminus can modulate the activity of this initiation factor in the absence of a cognate regulatory anti-σ factor. M. tuberculosis σ^J can bind promoter DNA in vitro; this interaction is substantially impaired by the removal of the SnoaL_2 domain. This finding is consistent with assays to evaluate σ^J-mediated gene expression. Structural similarity of the SnoaL_2 domain with epoxide hydrolases also suggests a novel functional role for this domain. The conserved sequence features between M. tuberculosis σ^J and other members of the ECF41 family of σ-factors suggest that the regulatory mechanism involving the C-terminal SnoaL_2 domain is likely to be retained in this family of proteins. These studies suggest that the ECF41 family of σ-factors incorporate features of both—the σ⁷⁰ family and bacterial one—component systems thereby providing a direct mechanism to implement environment-mediated transcription changes.

中文翻译：

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在稠合SnoaL_2域结核杆菌σσ因子^Ĵ调节启动子识别

细胞外功能（ECF）σ因子广泛存在于细菌中，将环境刺激与基因表达的变化联系在一起。这些转录因子跨越几个系统发育上不同的组，并且在它们的激活和调节机制上非常不同。在这里，我们描述了的结构和生化特征结核杆菌ECF因子σ ^Ĵ这表明，在C末端的SnoaL_2域可以调节在不存在同源调控抗σ因子的这个起始因子的活性。结核分枝杆菌σ ^Ĵ可以结合启动子的DNA在体外; SnoaL_2结构域的去除大大削弱了这种相互作用。这一发现与试验来评价σ一致^Ĵ -介导的基因表达。SnoaL_2结构域与环氧化物水解酶的结构相似性也表明该结构域具有新的功能。之间的保守序列特征结核分枝杆菌σ ^Ĵ和ECF41家族的σ因子的其他成员建议涉及的C-末端结构域SnoaL_2的调控机制可能在该蛋白家族的保留。这些研究表明，的ECF41家庭σ因子都-的σ的收纳功能⁷⁰ 家族和细菌的单组分系统，从而提供了一种直接的机制来实现环境介导的转录变化。