TraitMech

TraitMech › GENOMICS

Septu system

traitmech:000233 · CLASS · PROPOSED

A phage defense system in which an organism possesses a Septu locus encoding PtuA and the HNH endonuclease PtuB, whose PtuAB oligomer confers antiphage immunity through nuclease-mediated phage genome cleavage in standalone systems and can be regulated by retron RT-msDNA complexes in Retron-Septu loci.

Trait evidence (6)

  • DOI:10.1126/science.aar4120
    Septu PtuAB pfam13304, COG3950, pfam13395, pfam01844 ATPase, HNH nuclease 2,506 2,117 (4.1%)

    Doron et al. reported Septu/PtuAB as an ATPase- and HNH-nuclease-linked system in their pangenome-scale antiphage-system discovery screen.

  • DOI:10.1038/s41594-023-01172-8
    E. coli Septu system, an anti-phage defense system, comprises two components: PtuA and PtuB

    Yang et al. support defining Septu as a two-component PtuA/PtuB antiphage system.

  • DOI:10.1038/s41594-023-01172-8
    PtuA contains an ATPase domain while PtuB is a nuclease that belongs to the His-Asn-His (HNH) family

    Yang et al. support the ATPase and HNH endonuclease component classes that distinguish the PtuAB system.

  • DOI:10.1038/s41594-023-01172-8
    PtuAB restricts phage growth by cleaving phage genomic DNA

    Yang et al. connect the PtuAB complex to nuclease-mediated restriction of phage growth in cells.

  • DOI:10.1126/science.adv3344
    The Retron-Septu system uniquely integrates retron and Septu antiphage defenses

    Wang et al. support recognizing Retron-Septu as a Septu architecture with coupled retron regulation, not as a separate exact replacement for the broader Septu class.

  • DOI:10.1126/science.adv3344
    Activation occurs upon disassembly, releasing PtuAB, which degrades single-stranded DNA to restrict phage replication

    Wang et al. connect Retron-Septu activation to release of PtuAB and DNA degradation that restricts phage replication.

Septu PtuAB oligomers cleave phage genomic DNA

Evidence-backed process sketch linking a Septu locus to PtuAB oligomer assembly, PtuB-dependent nuclease activity, cleavage of phage genomic DNA, and inhibition of phage replication.

NONMECHANISTIC · The graph captures the shared PtuA/PtuB nuclease logic without asserting one exact activation trigger, ATP regulatory state, phage cue, target DNA modification, standalone-versus-retron architecture, or ssDNA-versus-genomic-DNA substrate across all Septu and Retron-Septu loci.

Septu PtuAB oligomers cleave phage genomic DNA Interactive directed graph showing evidence-backed causal relationships for Septu system.

Edge evidence

  • Septu locus contributes to PtuAB oligomer assembly RO:0002326

    The Septu locus encodes PtuA and PtuB components that assemble into a higher-order PtuAB complex.

    • DOI:10.1038/s41594-023-01172-8 PtuA and PtuB form a stable complex with a 6:2 stoichiometry Yang et al. support assembly of the PtuA and PtuB Septu components.
  • PtuAB oligomer assembly enables PtuAB antiphage activity RO:0002327

    PtuAB assembly is critical for antiphage activity.

    • DOI:10.1038/s41594-023-01172-8 the assembly of PtuAB is critical for its anti-phage activity Yang et al. support a functional connection between PtuAB assembly and antiphage activity.
  • PtuAB antiphage activity enables phage genomic DNA cleavage RO:0002327

    The PtuAB complex restricts phage growth by cleaving phage genomic DNA.

    • DOI:10.1038/s41594-023-01172-8 E. coli anti-phage defense mediated by PtuAB via degrading the phage genomic DNA Yang et al. connect PtuAB activity to cleavage of phage genomic DNA.
  • phage genomic DNA cleavage mitigates phage growth METPO:2007407

    PtuAB-mediated cleavage of phage genomic DNA restricts phage growth.

    • DOI:10.1038/s41594-023-01172-8 PtuAB restricts phage growth by cleaving phage genomic DNA Yang et al. connect PtuAB nuclease activity to reduced phage growth.
  • phage genomic DNA cleavage confers Septu system METPO:2007700

    PtuAB-mediated phage genomic DNA cleavage realizes the Septu system trait.

    • DOI:10.1038/s41594-023-01172-8 PtuAB can confer bacteria immune defense against phage infection by digesting phage genomic DNA in a species-dependent way Yang et al. support the DNA-digestion logic of PtuAB antiphage defense.
  • Septu system is a phage defense system rdfs:subClassOf

    Septu system possession is a phage-defense-system trait.

    • DOI:10.1126/science.aar4120 Septu PtuAB pfam13304, COG3950, pfam13395, pfam01844 ATPase, HNH nuclease 2,506 2,117 (4.1%) Doron et al. reported Septu in a table of candidate antiphage defense systems.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1038/s41594-023-01172-8

Parent traits (1)

Synonyms (1)

  • Septu EXACT_SYNONYM · DOI:10.1126/science.aar4120

kg-microbe context

No kg-microbe node embedding matched this record in the 2026-04-25 deepwalk.

Canonical examples (1)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

  • Escherichia coli NCBITaxon:562 DOI:10.1038/s41594-023-01172-8 Yang et al. structurally and functionally characterized an Escherichia coli Septu system in which PtuA and PtuB assemble into a 6:2 oligomer that restricts phage growth by cleaving phage genomic DNA.

Discussions and Knowledge Gaps (1)

Open questions attached to this trait. Seeded by just knowledge-gap-scan and curated; see the corpus-wide index.

Resolve standalone Septu activation, Retron-Septu release, and DNA-substrate specificity before minting narrower Septu mechanism children.

KNOWLEDGE GAP OPEN septu-standalone-retron-regulation-gap · raised by codex · 2026-09-15

Not yet attached to a section of this record — a curator sets attaches_to (e.g. causal_graphs#some_edge) so the gap shows beside the mechanism it concerns.

Yang et al. support a standalone Escherichia coli PtuAB system in which ATP modulates PtuA/PtuB nuclease activity through an incompletely resolved phage trigger, and Wang et al. support Retron-Septu Ec83/Ec78 complexes in which retron RT-msDNA association keeps PtuAB inactive until disassembly. The first TraitRecord therefore stays at the PtuA/PtuB system level until separate review resolves standalone activation, retron-dependent release, target DNA classes, and phage-specific activity across Septu loci.

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    Minted Septu system as a DOI-backed GENOMICS TraitRecord under the phage defense system parent after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v110.