Shi Jing, Ye Zonghang, Feng Zhenzhen, Wen Aijia, Wang Lu, Zhang Zhipeng, Xu Liqiao, Song Qian, Wang Fulin, Liu Tianyu, Wang Shuang, Feng Yu, Lin Wei
School of Medicine, Nanjing University of Chinese Medicine, Nanjing Drum Tower Hospital, Nanjing 210023, China.
Department of Biophysics, and Department of Infectious Disease of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.
iScience. 2024 Jun 29;27(8):110421. doi: 10.1016/j.isci.2024.110421. eCollection 2024 Aug 16.
The antibiotic regulatory proteins (SARPs) are ubiquitously distributed transcription activators in and control antibiotics biosynthesis and morphological differentiation. However, the molecular mechanism behind SARP-dependent transcription initiation remains elusive. We here solve the cryo-EM structure of an AfsR-loading RNA polymerase (RNAP)-promoter intermediate complex (AfsR-RPi) including the RNAP, a large SARP member AfsR, and its target promoter DNA that retains the upstream portion straight. The structure reveals that one dimeric N-terminal AfsR-SARP domain (AfsR-SARP) specifically engages with the same face of the AfsR-binding sites by the conserved DNA-binding domains (DBDs), replacing σR4 to bind the suboptimal -35 element, and shortens the spacer between the -10 and -35 elements. Notably, the AfsR-SARPs also recruit RNAP through extensively interacting with its conserved domains (β flap, σR4, and αCTD). Thus, these macromolecular snapshots support a general model and provide valuable clues for SARP-dependent transcription activation in .
抗生素调控蛋白（SARPs）是广泛分布于链霉菌中的转录激活因子，控制抗生素生物合成和形态分化。然而，SARP依赖的转录起始背后的分子机制仍然不清楚。我们在此解析了一个AfsR加载的RNA聚合酶（RNAP）-启动子中间体复合物（AfsR-RPi）的冷冻电镜结构，该复合物包括RNAP、一个大型SARP成员AfsR及其靶启动子DNA，该DNA保留了上游部分呈直线状。该结构揭示，一个二聚体的N端AfsR-SARP结构域（AfsR-SARP）通过保守的DNA结合结构域（DBDs）与AfsR结合位点的同一面特异性结合，取代σR4以结合次优的-35元件，并缩短了-10和-35元件之间的间隔。值得注意的是，AfsR-SARPs还通过与其保守结构域（β翼、σR4和αCTD）广泛相互作用来招募RNAP。因此，这些大分子结构快照支持了一个通用模型，并为链霉菌中SARP依赖的转录激活提供了有价值的线索。
