Kev Laboratory of Microbial Pathogenesis and Interventions of Fuian Province University, the Key Laboratory of inmate lmmune Biology of Fuijian Province, Biomedical Research Center of South China, Key Laboratory of Opto Electronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China.
State Key Laboratory of Respiratory Disease, Guangzhou Chest Hospital, Institute of Tuberculosis, Guangzhou Medical University, Guangdong, 510095, P. R. China.
Nat Commun. 2024 Oct 27;15(1):9269. doi: 10.1038/s41467-024-53614-6.
Sir2-HerA is a widely distributed antiphage system composed of a RecA-like ATPase (HerA) and an effector with potential NADase activity (Sir2). Sir2-HerA is believed to provide defense against phage infection in Sir2-dependent NAD depletion to arrest the growth of infected cells. However, the detailed mechanism underlying its antiphage activity remains largely unknown. Here, we report functional investigations of Sir2-HerA from Staphylococcus aureus (SaSir2-HerA), unveiling that the NADase function of SaSir2 can be allosterically activated by the binding of SaHerA, which then assembles into a supramolecular complex with NADase activity. By combining the cryo-EM structure of SaSir2-HerA in complex with the NAD cleavage product, it is surprisingly observed that Sir2 protomers that interact with HerA are in the activated state, which is due to the opening of the α15-helix covering the active site, allowing NAD to access the catalytic pocket for hydrolysis. In brief, our study provides a comprehensive view of an allosteric activation mechanism for Sir2 NADase activity in the Sir2-HerA immune system.
Sir2-HerA 是一种广泛分布的抗噬菌体系统，由 RecA 样 ATP 酶（HerA）和具有潜在 NADase 活性的效应物（Sir2）组成。Sir2-HerA 被认为可以提供针对依赖 Sir2 的 NAD 消耗的噬菌体感染的防御，以阻止感染细胞的生长。然而，其抗噬菌体活性的详细机制在很大程度上仍然未知。在这里，我们报告了金黄色葡萄球菌（SaSir2-HerA）中 Sir2-HerA 的功能研究，揭示了 SaSir2 的 NADase 功能可以通过 SaHerA 的结合进行别构激活，然后组装成具有 NADase 活性的超分子复合物。通过将 SaSir2-HerA 与 NAD 裂解产物的冷冻电镜结构结合，令人惊讶地观察到与 HerA 相互作用的 Sir2 原聚体处于激活状态，这是由于覆盖活性位点的α15-螺旋的打开，允许 NAD 进入催化口袋进行水解。总之，我们的研究提供了 Sir2-HerA 免疫系统中 Sir2 NADase 活性的别构激活机制的全面视图。
