SNIPE: Membrane-Bound Nuclease Anti-Phage Defence

IN_PROGRESS BIOLOGY_DOMAIN

Species: ECOLX

Genes: SNIPE

Warnings (1)

SNIPE: Membrane-Bound Nuclease Anti-Phage Defence

Bottom line: SNIPE is a bacterial inner-membrane nuclease that cuts phage DNA while it is
being injected, using the phage's own tape measure protein to position its GIY-YIG nuclease at
the injection site (Saxton et al. 2026, Nature). It tells self from non-self by location
rather than by DNA sequence (CRISPR) or modification (restriction-modification). We wrote a
full gene review of the E. coli protein (A0A8T9CRB7), which had no GO annotations at all,
and proposed seven annotations from the paper's direct evidence, including DNA endonuclease
activity and defense response to virus, plus two new process terms. We did this because
SNIPE homologues occur in about a third of well-sequenced bacterial clades, and existing GO
cannot place it: the anti-phage nucleic-acid branch is framed as clearance of intracellular
DNA, and neither CRISPR-Cas nor restriction-modification sits under defense response to
virus. A draft GO issue makes that case,
but no filed issue number is recorded; the
review is still DRAFT, and the homologue GO-annotation audit, DefenseFinder cross-check,
InterPro2GO submission, and IPR025280 literature-link tasks remain open.

Overview

SNIPE (Surface-associated Nuclease Inhibiting Phage Entry) is a bacterial anti-phage defence system that cleaves phage DNA during genome injection. It represents a novel self/non-self discrimination strategy in prokaryotic immunity, distinct from CRISPR-Cas (sequence recognition) and restriction-modification (DNA modification recognition). SNIPE exploits the spatial organization of phage genome injection — the fact that phage DNA must pass through the cell membrane — to specifically target foreign DNA.

Key paper: Saxton DS, DeWeirdt PC, Doering CR, Roney IJ & Laub MT (2026). A membrane-bound nuclease directly cleaves phage DNA during genome injection. Nature. https://doi.org/10.1038/s41586-026-10207-1

Previous identification: Vassallo CN, Doering CR, Littlehale ML, Teodoro GIC & Laub MT (2022). A functional selection reveals previously undetected anti-phage defence systems in the E. coli pangenome. Nat. Microbiol. 7:1568-1579. (Originally named PD-lambda-1.)

Mechanism

  1. SNIPE is a ~500 aa inner membrane protein with three domains:
  2. N-terminal transmembrane domain (aa 5-24): anchors to inner membrane
  3. DUF4041 domain (aa ~144-262): binds DNA; interacts with phage tape measure proteins (TMPs)
  4. GIY-YIG nuclease domain (aa ~357-450): cleaves phage DNA (catalytic residue E414)
  5. SNIPE pre-associates with ManYZ (mannose permease) in the inner membrane before infection
  6. During phage genome injection, DUF4041 binds the phage tape measure protein, positioning the nuclease to cleave incoming DNA
  7. This provides direct defence — the infected cell survives (unlike abortive infection systems)
  8. SNIPE also provides ManYZ-independent defence against siphoviruses via weak TMP interactions

InterPro / Pfam

Key Proteins

SNIPE (PD-lambda-1)

E. coli host proteins involved

Protein UniProt Role in SNIPE mechanism
ManY P69801 Inner membrane permease; SNIPE pre-associates with ManYZ complex
ManZ P69805 Inner membrane permease; part of genome injection apparatus for lambda
ManX P69797 Mannose PTS EIIAB component
LamB P02943 Outer membrane maltoporin; lambda receptor
OmpF P02931 Outer membrane porin; alternative receptor for generalist lambda

Phage lambda proteins

Protein UniProt Role
gpH (TMP) P03736 Tape measure protein; SNIPE target during genome injection
gpJ P03749 Tail tip protein; host specificity

Evolutionary Diversity of SNIPE Homologues

SNIPE homologues show a modular architecture with highly diversified N-terminal regions:
- 59% harbour one transmembrane domain
- 7% harbour two transmembrane domains
- 34% lack predicted TM domains — these use alternative membrane-targeting strategies:
- DivIVA domains (negative membrane curvature binding)
- Type III secretion system domains
- Pleckstrin homology domains (phospholipid binding)
- Phage tail protein fusions

The GIY-YIG nuclease domain is the most conserved region. The DUF4041 domain shows moderate conservation with a positively charged DNA-binding interface. The N-terminal region has the highest variability, suggesting it functions as an adapter for phage specificity.

GO Annotation Considerations

GO terms proposed for SNIPE

Annotation challenges

  1. No existing GO term captures "cleavage of foreign DNA during membrane injection"
  2. The DUF4041 domain has dual function (DNA binding + TMP binding), but its TMP interaction may be better captured in GO-CAM than by a generic protein-binding annotation
  3. Direct defence vs. abortive infection distinction matters for BP annotation
  4. The ManYZ interaction is pre-infection positioning, not a canonical "protein complex"

Proposed new GO terms in the review

InterPro2GO Strategy for SNIPE

IPR025280 / PF13250 captures the SNIPE-associated DUF4041 domain, not the
complete anti-phage nuclease architecture. The architecture analysis found 1,612
IPR025280 proteins; 1,466 of them also carry a GIY-YIG-like catalytic co-feature
(PF13455 or PF10544 / IPR018306), and 990 have an N-terminal TM-like signal.

InterPro2GO mapping should therefore avoid direct IPR025280-only propagation to
DNA endonuclease activity or plasma membrane terms. A conservative SNIPE rule should
require IPR025280 plus PF13455 or PF10544 / IPR018306, plus membrane-targeting
evidence such as an N-terminal TM/signal feature, IPR007829, or IPR039519, with
IPR018929 treated as optional lower-confidence support.

DivIVA membrane anchoring (BACSU)

genes/BACSU/divIVA/divIVA-ai-review.yaml (P71021) — ~34% of SNIPE homologues lacking transmembrane domains use DivIVA-like domains for membrane anchoring. The DivIVA review covers the same membrane curvature-sensing mechanism these SNIPE variants use.

Phage-bacteria arms race genes

Gene Organism File Relevance to SNIPE
darB Phage P1 (9CAUD) genes/9CAUD/darB/darB-ai-review.yaml Antirestriction protein ejected into host to protect phage DNA from Type I R-M. SNIPE is the host-side counterpart
DAM Phage T4 (BPT4) genes/BPT4/DAM/DAM-ai-review.yaml DNA adenine methyltransferase protecting phage DNA from host restriction
AcrF8 Phage ZF40 (BPZF4) genes/BPZF4/AcrF8/AcrF8-ai-review.yaml Anti-CRISPR protein — another phage counter-defence strategy
AimP Phage phi3T (BPPHT) genes/BPPHT/AimP/AimP-falcon-research.md Phage quorum sensing peptide governing lysis-lysogeny decisions
Project File Connection
Anti-CRISPR projects/ANTI_CRISPR.md Parallel bacterial defence systems and phage counter-strategies
SPKW-BPT4 projects/SPKW/SPKW-BPT4.md Annotation challenges for phage-bacteria interactions
cGAS-STING projects/CGAS_STING_PATHWAY.md Eukaryotic cytosolic DNA sensing; conceptual parallel (cGAS senses foreign DNA in cytoplasm; SNIPE intercepts it at the membrane)
Surveillance Immunity projects/CAEEL_SURVEILLANCE_IMMUNITY.md Innate immunity via spatial/contextual detection rather than sequence recognition

Genes for Review

Species Gene UniProt Status
ECOLX (wild) SNIPE/PD-lambda-1 A0A8T9CRB7 DRAFT

Key References

STATUS

Completed

Pending

NOTES

2026-03-01

Project Creation

Created from reading Saxton et al. (2026) Nature paper on SNIPE.

Key observations:
- IPR025280 (formerly DUF4041) has already been renamed to "SNIPE associated domain" in InterPro, with description updated to reference the cleavage mechanism. This suggests InterPro curators updated the entry around publication.
- SNIPE represents a genuinely novel immune mechanism — not sequence-based (like CRISPR) or modification-based (like R-M), but localization-based.
- Conceptual parallel to eukaryotic IFITM proteins that block viral entry at membranes.
- The modular N-terminal diversity across ~500 homologues is an interesting case for studying domain shuffling and functional diversification.