Bacterial immune activation via supramolecular assembly with phage triggers
Article meta
Article Date: 04 February 2026
Article URL: https://www.nature.com/articles/s41586-025-10060-8
Article Image: Figure 1
Summary
This Nature study identifies and characterises a bacterial antiphage system named RAZR. The protein assembles into large supramolecular complexes around ring-shaped phage proteins — notably a 24-mer phage protein Gp77 and dodecameric portal proteins from T3/T7/SECΦ18 — triggering RNase activity that aborts infection. RAZR contains an N-terminal zinc-finger domain (ZFD) that senses phage triggers and a C-terminal HEPN-like RNase domain that cleaves single-stranded RNA, shutting down translation and killing the infected cell to block phage spread. Cryo-EM, biochemistry, genetics and RNA-seq support a model where RAZR polymerises circumferentially around phage protein rings to reposition HEPN active sites and drive broad RNA cleavage.
Key Points
- RAZR is a bacterial antiphage system composed of a ZFD sensor and a HEPN-like RNase effector that uses abortive infection to block phage spread.
- Activation is triggered by structurally unrelated phage proteins that form ring scaffolds — Gp77 (24-mer) and portal proteins (12-mer) — allowing recognition by geometry rather than strict sequence homology.
- Cryo-EM shows RAZR assembles into a multi-layered ring complex (~1.4 MDa) with ZFDs contacting the inner phage ring and HEPN domains arranged outward to form active RNase sites.
- Once activated, RAZR nonspecifically cleaves single-stranded RNAs (mRNAs, tRNAs and rRNAs), rapidly inhibiting translation and leading to host-cell death (abortive infection).
- ZFD sequence variation dictates phage specificity: swapping ZFDs between homologues alters the spectrum of protected phages.
- Higher-order oligomerisation (beyond HEPN dimers) and an interdomain linker are critical for activation; mutations that disrupt oligomer interfaces abolish defence.
- Sensing by ring geometry helps avoid autoimmunity because similarly sized host rings are absent or different in size.
Content summary
The authors characterised a RAZR system discovered in an E. coli isolate. RAZR has a zinc-finger N-terminal domain for sensing and a DUF4145/HEPN-like C-terminal RNase domain. Genetic screens isolated phage escape mutants mapping to either a phage recombination protein (Gp77) or to portal proteins in unrelated phages, indicating multiple triggers. Biochemistry showed RAZR and triggers form very large complexes; cryo-EM reconstructions revealed concentric rings with 24 copies of Gp77 surrounded by 12 RAZR dimers and an outer HEPN ring. Mutational analysis of interface residues validated the binding surfaces. Functional assays (pulse-labelling, in vitro translation, RNA gels and RNA-seq) demonstrated that activated RAZR cleaves ssRNA broadly (mRNA, tRNA, rRNA), stalling translation and effecting abortive infection. Swapping the ZFD between homologues reprogrammes phage specificity. Overall, RAZR senses ring-shaped phage assemblies and oligomerises to activate RNase-mediated defence.
Context and relevance
This work links bacterial innate immunity to a theme well-known in eukaryotes: supramolecular assembly as an activation mechanism. It expands our understanding of how bacteria detect phages — not only via small-molecule messengers or single protein recognitions, but by recognising supramolecular geometry (protein rings). The study is relevant to researchers in microbiology, structural biology and host–pathogen interactions: it reveals a broadly applicable detection strategy (geometry-templated activation) and a destructive RNase effector that can be tuned by the ZFD. It also informs phage–host coevolution and could influence synthetic biology uses of programmable abortive-infection modules or anti-phage strategies for industrial strains.
Why should I read this?
Look — if you care about how bacteria actually spot phages and shut them down, this paper is like the missing chapter. It shows a clever trick: instead of recognising sequences, the bacterial sensor wraps itself around phage-made protein rings and flips on a killing RNase. If you work with phages, bacterial immunity or want modular defence tools, the nitty-gritty here will save you time and spark ideas.
Author style
Punchy: this is a high-impact, structurally rigorous demonstration that bacteria use supramolecular templating to activate toxic RNases. If you’re in the field, the detailed cryo-EM, mutational validation and RNA-seq results are essential — they convincingly connect geometry-sensing to function and specificity.