Nature Communications, 13 October, 2023, DOI：https://doi.org/10.1038/s41467-023-41796-4

Structure of the transcription open complex of distinct σI factors

Jie Li, Haonan Zhang, Dongyu Li, Ya-Jun Liu, Edward A. Bayer, Qiu Cui, Yingang Feng & Ping Zhu

Abstract

Bacterial σ^I factors of the σ⁷⁰-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^I 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 σI 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 σI paralogues were further revealed by comparison of the two structures. Consequently, the σ^I factors represent a distinct set of the σ⁷⁰-family σ factors, thus highlighting the diversity of bacterial transcription.

Article link：https://www.nature.com/articles/s41467-023-41796-4