Structure and mechanism of antiphage retron Eco2.

ABSTRACT: Retrons are prokaryotic reverse transcriptase systems that produce multicopy single-stranded DNA (msDNA), yet the principles by which they mediate antiviral defense remain largely unresolved. Here we investigate the mechanism of Escherichia coli Eco2, a minimal retron composed of a single reverse transcriptase-nuclease fusion protein. Cryogenic electron microscopy and hydrogen/deuterium exchange mass spectrometry reveal the structures and dynamics of a trimeric nucleoprotein complex assembled within a branched msDNA scaffold, which cages the TOPRIM nucleases. We show that the phage-encoded endonuclease DenB initiates msDNA degradation, thereby unblocking the nuclease active sites. Activated Eco2 cuts transfer RNAs, resulting in translational shutdown for antiphage defense. We further ident

SUBMITTER: Jasnauskaite M 

PROVIDER: S-EPMC12916289 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature