期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：10
页码：E1805-E1814
DOI：10.1073/pnas.1619464114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The bacterial σ factors confer promoter specificity to the RNA polymerase (RNAP). One alternative σ factor, σN, is unique in its structure and functional mechanism, forming transcriptionally inactive promoter complexes that require activation by specialized AAA+ ATPases. We report a 3.4-Å resolution X-ray crystal structure of a σN fragment in complex with its cognate promoter DNA, revealing the molecular details of promoter recognition by σN. The structure allowed us to build and refine an improved σN-holoenzyme model based on previously published 3.8-Å resolution X-ray data. The improved σN-holoenzyme model reveals a conserved interdomain interface within σN that, when disrupted by mutations, leads to transcription activity without activator intervention (so-called bypass mutants). Thus, the structure and stability of this interdomain interface are crucial for the role of σN in blocking transcription activity and in maintaining the activator sensitivity of σN.
