9KK2

Cryo-EM structure of the Retron-Eco7 complex (state 5)

9KK2 の概要

• エントリーDOI: 10.2210/pdb9kk2/pdb
• EMDBエントリー: 62382
• 分子名称: RNA-directed DNA polymerase, AAA family ATPase, TIGR02646 family protein, ... (8 entities in total)
• 機能のキーワード: retron, reverse transcriptase, rna binding protein
• 由来する生物種: Escherichia coli; 詳細
• タンパク質・核酸の鎖数: 12
• 化学式量合計: 525476.61

構造登録者

Ishikawa, J.,Yoneyama, K.,Yamashita, K.,Nishimasu, H. (登録日: 2024-11-12, 公開日: 2025-11-12, 最終更新日: 2025-12-17)

主引用文献

Ishikawa, J.,Yoneyama, K.,Azam, A.H.,Nagao, A.,Mitsuda, Y.,Nakazaki, R.,Chihara, K.,Hiraizumi, M.,Yamashita, K.,Suzuki, T.,Kiga, K.,Nishimasu, H.
Structural mechanism of the Retron-Eco7 anti-phage defense system.
Nat Commun, 16:10821-10821, 2025

PubMed Abstract: Retrons are prokaryotic genetic elements involved in anti-phage defense and consist of a non-coding RNA, a reverse transcriptase (RT), and various effector proteins. Retron-Eco7 (previously known as Retron-Ec78) from Escherichia coli encodes two effector proteins (the PtuA ATPase and the PtuB nuclease) and degrades the host tRNA upon phage infection, thereby protecting host cells against invading phages. However, its defense mechanism remains elusive. Here, we report the cryo-electron microscopy (cryo-EM) structures of the Retron-Eco7 complex, comprising the RT, multicopy single-stranded DNA (msDNA), PtuA, and PtuB. The Retron-Eco7 structures reveal that the RT-msDNA complex associates with two PtuA-PtuB complexes, potentially inhibiting their nuclease activity and suppressing bacterial growth arrest prior to phage infection. Furthermore, the phage-encoded D15 nuclease acts as a trigger for the Retron-Eco7 system and cleaves the msDNA bound to the complex, facilitating the dissociation of PtuA-PtuB from RT-msDNA. Our data indicate that msDNA cleavage by D15 is the initial step required for the specific cleavage of the host tRNA by the PtuA-PtuB nuclease, which leads to abortive infection. Overall, this study provides mechanistic insights into the Retron-Eco7 system and highlights the diversity of prokaryotic anti-phage defense mechanisms.

PubMed: 41330933
DOI: 10.1038/s41467-025-66589-9

実験手法

ELECTRON MICROSCOPY (2.58 Å)