Conte Amy N, Ruchel Madison E, Ridgeway Samantha M, Kibby Emily M, Nagy Toni A, Whiteley Aaron T
Department of Biochemistry, University of Colorado Boulder, Boulder, Colorado, United States of America.
Department of Biology, Front Range Community College, Longmont, Colorado, United States of America.
PLoS Biol. 2025 May 30;23(5):e3003203. doi: 10.1371/journal.pbio.3003203.
Bacteria encode a wide range of antiphage systems and a subset of these proteins are homologous to components of the human innate immune system. Mammalian nucleotide-binding and leucine-rich repeat containing proteins (NLRs) and bacterial NLR-related proteins use a central NACHT domain to link detection of infection with initiation of an antimicrobial response. Bacterial NACHT proteins provide defense against both DNA and RNA phages. Here we investigate the mechanism of phage detection by the bacterial NLR-related protein bNACHT25 in E. coli. bNACHT25 was specifically activated by Emesvirus ssRNA phages and analysis of MS2 phage escaper mutants that evaded detection revealed a critical role for Coat Protein (CP). A genetic assay showed CP was sufficient to activate bNACHT25 but the two proteins did not directly interact. Instead, we found bNACHT25 requires the host chaperone DnaJ to detect CP and protect against phage. Our data support a model in which bNACHT25 detects a wide range of phages using an indirect mechanism that may involve guarding a host cell process rather than binding a specific phage-derived molecule.
细菌编码多种抗噬菌体系统，其中一部分蛋白质与人类先天免疫系统的组成部分同源。哺乳动物含核苷酸结合和富含亮氨酸重复序列的蛋白质（NLRs）以及细菌NLR相关蛋白利用中央NACHT结构域将感染检测与抗菌反应的启动联系起来。细菌NACHT蛋白对DNA和RNA噬菌体均提供防御。在此，我们研究大肠杆菌中细菌NLR相关蛋白bNACHT25检测噬菌体的机制。bNACHT25被埃姆斯病毒单链RNA噬菌体特异性激活，对逃避检测的MS2噬菌体逃逸突变体的分析揭示了外壳蛋白（CP）的关键作用。一项遗传学检测表明CP足以激活bNACHT25，但这两种蛋白质并未直接相互作用。相反，我们发现bNACHT25需要宿主分子伴侣DnaJ来检测CP并抵御噬菌体。我们的数据支持一种模型，即bNACHT25使用一种间接机制检测多种噬菌体，该机制可能涉及守护宿主细胞过程而非结合特定的噬菌体衍生分子。
