CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101, Qingdao, Shandong, China.
Shandong Provincial Key Laboratory of Synthetic Biology, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266101, Qingdao, Shandong, China.
Nat Commun. 2023 Oct 13;14(1):6455. doi: 10.1038/s41467-023-41796-4.
Bacterial σ factors of the σ-family are widespread in Bacilli and Clostridia and are involved in the heat shock response, iron metabolism, virulence, and carbohydrate sensing. A multiplicity of σ paralogues in some cellulolytic bacteria have been shown to be responsible for the regulation of the cellulosome, a multienzyme complex that mediates efficient cellulose degradation. Here, we report two structures at 3.0 Å and 3.3 Å of two transcription open complexes formed by two σ factors, SigI1 and SigI6, respectively, from the thermophilic, cellulolytic bacterium, Clostridium thermocellum. These structures reveal a unique, hitherto-unknown recognition mode of bacterial transcriptional promoters, both with respect to domain organization and binding to promoter DNA. The key characteristics that determine the specificities of the σ paralogues were further revealed by comparison of the two structures. Consequently, the σ factors represent a distinct set of the σ-family σ factors, thus highlighting the diversity of bacterial transcription.
芽孢杆菌和梭菌中广泛存在 σ 家族的细菌 σ 因子，它们参与热休克反应、铁代谢、毒力和碳水化合物感应。一些纤维素分解菌中的多种 σ 同源物已被证明负责调节细胞体，细胞体是一种介导有效纤维素降解的多酶复合物。在这里，我们报告了来自嗜热纤维素分解菌嗜热梭菌的两个 σ 因子 SigI1 和 SigI6 分别形成的两个转录开放复合物的 3.0 Å 和 3.3 Å 的两个结构。这些结构揭示了细菌转录启动子的独特的、迄今为止未知的识别模式，无论是在结构域组织还是与启动子 DNA 的结合方面。通过比较这两个结构，进一步揭示了决定 σ 同源物特异性的关键特征。因此，σ 因子代表了一组独特的 σ 家族 σ 因子，从而突出了细菌转录的多样性。
