9X9B

Retron-Eco8 complex with ATP-Mg2+

Summary for 9X9B

• Entry DOI: 10.2210/pdb9x9b/pdb
• EMDB information: 66663
• Descriptor: Retron Eco8 reverse transcriptase, Retron Eco8 OLD nuclease, RNA (82-MER), ... (6 entities in total)
• Functional Keywords: complex, rna binding protein/rna/dna, rna binding protein-rna-dna complex
• Biological source: Escherichia coli; More
• Total number of polymer chains: 16
• Total formula weight: 732257.82

Authors

Yu, Y.,Chen, Q. (deposition date: 2025-10-20, release date: 2026-03-04)

Primary citation

Xiong, C.,Pu, H.,Tang, Y.,Liu, T.,Luo, D.,Chen, Q.,Yu, Y.
Structural basis of Retron-Eco8-mediated antiphage defense.
Nucleic Acids Res., 54:-, 2026

PubMed Abstract: Retrons represent a novel class of bacterial defense systems that employ reverse transcriptase (RT), noncoding RNA, and effector proteins to counteract phage infections. In this study, we elucidate the molecular mechanism of a retron system, Retron-Eco8. Biochemical experiments reveal that the Retron-Eco8 holocomplex, rather than the effector alone, exhibits double-stranded DNA cleavage activity, triggering abortive infection and therefore effectively halting phage propagation. Cryo-electron microscopy (cryo-EM) analysis reveals a supramolecular assembly comprising four RT subunits, four multicopy single-stranded DNA molecules, and four overcoming lysogenization defect (OLD) nucleases-a configuration critical for antiphage defense. Notably, we examine the activation of Retron-Eco8 by diverse single-stranded DNA-binding (SSB) proteins, and phylogenetic analysis of these SSB proteins elucidates the phage resistance specificity. Collectively, our findings delineate the structural architecture of the Retron-Eco8 defense complex and provide mechanistic insights into retron-mediated bacterial immunity.

PubMed: 41665008
DOI: 10.1093/nar/gkag111

Experimental method

ELECTRON MICROSCOPY (2.8 Å)