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Finocchio G, Koopal B, Potocnik A, Heijstek C, Westphal AH, Jinek M, Swarts DC. Target DNA-dependent activation mechanism of the prokaryotic immune system SPARTA. Nucleic Acids Res 2024; 52:2012-2029. [PMID: 38224450 PMCID: PMC10899771 DOI: 10.1093/nar/gkad1248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 01/16/2024] Open
Abstract
In both prokaryotic and eukaryotic innate immune systems, TIR domains function as NADases that degrade the key metabolite NAD+ or generate signaling molecules. Catalytic activation of TIR domains requires oligomerization, but how this is achieved varies in distinct immune systems. In the Short prokaryotic Argonaute (pAgo)/TIR-APAZ (SPARTA) immune system, TIR NADase activity is triggered upon guide RNA-mediated recognition of invading DNA by an unknown mechanism. Here, we describe cryo-EM structures of SPARTA in the inactive monomeric and target DNA-activated tetrameric states. The monomeric SPARTA structure reveals that in the absence of target DNA, a C-terminal tail of TIR-APAZ occupies the nucleic acid binding cleft formed by the pAgo and TIR-APAZ subunits, inhibiting SPARTA activation. In the active tetrameric SPARTA complex, guide RNA-mediated target DNA binding displaces the C-terminal tail and induces conformational changes in pAgo that facilitate SPARTA-SPARTA dimerization. Concurrent release and rotation of one TIR domain allow it to form a composite NADase catalytic site with the other TIR domain within the dimer, and generate a self-complementary interface that mediates cooperative tetramerization. Combined, this study provides critical insights into the structural architecture of SPARTA and the molecular mechanism underlying target DNA-dependent oligomerization and catalytic activation.
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Affiliation(s)
- Giada Finocchio
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Balwina Koopal
- Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, the Netherlands
| | - Ana Potocnik
- Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, the Netherlands
| | - Clint Heijstek
- Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, the Netherlands
| | - Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, the Netherlands
| | - Martin Jinek
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Daan C Swarts
- Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, the Netherlands
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Zhen X, Xu X, Ye L, Xie S, Huang Z, Yang S, Wang Y, Li J, Long F, Ouyang S. Structural basis of antiphage immunity generated by a prokaryotic Argonaute-associated SPARSA system. Nat Commun 2024; 15:450. [PMID: 38200015 PMCID: PMC10781750 DOI: 10.1038/s41467-023-44660-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 12/26/2023] [Indexed: 01/12/2024] Open
Abstract
Argonaute (Ago) proteins are ubiquitous across all kingdoms of life. Eukaryotic Agos (eAgos) use small RNAs to recognize transcripts for RNA silencing in eukaryotes. In contrast, the functions of prokaryotic counterparts (pAgo) are less well known. Recently, short pAgos in conjunction with the associated TIR or Sir2 (SPARTA or SPARSA) were found to serve as antiviral systems to combat phage infections. Herein, we present the cryo-EM structures of nicotinamide adenine dinucleotide (NAD+)-bound SPARSA with and without nucleic acids at resolutions of 3.1 Å and 3.6 Å, respectively. Our results reveal that the APAZ (Analogue of PAZ) domain and the short pAgo form a featured architecture similar to the long pAgo to accommodate nucleic acids. We further identified the key residues for NAD+ binding and elucidated the structural basis for guide RNA and target DNA recognition. Using structural comparisons, molecular dynamics simulations, and biochemical experiments, we proposed a putative mechanism for NAD+ hydrolysis in which an H186 loop mediates nucleophilic attack by catalytic water molecules. Overall, our study provides mechanistic insight into the antiphage role of the SPARSA system.
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Affiliation(s)
- Xiangkai Zhen
- Key Laboratory of Microbial Pathogenesis and Interventions of Fujian Province University, the Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China
| | - Xiaolong Xu
- Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, China Wuhan University, Wuhan, 430071, China
| | - Le Ye
- Key Laboratory of Microbial Pathogenesis and Interventions of Fujian Province University, the Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China
| | - Song Xie
- College of Chemistry, Fuzhou University, 350116, Fuzhou, China
| | - Zhijie Huang
- Key Laboratory of Microbial Pathogenesis and Interventions of Fujian Province University, the Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China
| | - Sheng Yang
- Key Laboratory of Microbial Pathogenesis and Interventions of Fujian Province University, the Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China
| | - Yanhui Wang
- Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, China Wuhan University, Wuhan, 430071, China
| | - Jinyu Li
- College of Chemistry, Fuzhou University, 350116, Fuzhou, China.
| | - Feng Long
- Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (Ministry of Education), School of Pharmaceutical Sciences, Department of Neurosurgery, Zhongnan Hospital of Wuhan University, Wuhan, China Wuhan University, Wuhan, 430071, China.
| | - Songying Ouyang
- Key Laboratory of Microbial Pathogenesis and Interventions of Fujian Province University, the Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, China.
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