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Kiwa system

traitmech:000231 · CLASS · PROPOSED

A phage defense system in which an organism possesses a two-component Kiwa locus encoding the transmembrane sensor KwaA and DNA-binding effector KwaB that assemble into a membrane-associated supercomplex and coordinate phage-attachment sensing with inhibition of phage DNA replication and late transcription.

Trait evidence (6)

  • DOI:10.1126/science.aar4120
    Kiwa KwaAB pfam16162 No annotated domain 934 924 (1.8%) Membrane associated

    Doron et al. reported Kiwa/KwaAB as a membrane-associated defense system in their pangenome-scale antiphage-system discovery screen.

  • DOI:10.1016/j.cell.2025.07.002
    Kiwa, a widespread two-component system composed of the transmembrane sensor KwaA and the DNA-binding effector KwaB

    Zhang et al. support defining Kiwa as a recurring two-component KwaA/KwaB antiviral system.

  • DOI:10.1016/j.cell.2025.07.002
    KwaA and KwaB assemble into a large, membrane-associated supercomplex

    Zhang et al. connect the KwaA and KwaB components to membrane-associated supercomplex assembly.

  • DOI:10.1016/j.cell.2025.07.002
    Upon phage binding, KwaA senses infection at the membrane, leading to KwaB binding of ejected phage DNA and inhibition of replication and late transcription, without inducing host cell death

    Zhang et al. connect phage binding to KwaA-dependent membrane sensing, KwaB binding of phage DNA, and inhibition of phage replication and late transcription.

  • DOI:10.1016/j.cell.2025.07.002
    its antiviral activity requires association with KwaA, suggesting spatial or conformational regulation

    Zhang et al. support KwaA-KwaB association as required for Kiwa antiviral activity.

  • DOI:10.1016/j.cell.2025.07.002
    Kiwa coordinates membrane-associated detection of phage infection with downstream DNA binding by its effector, forming a spatially coordinated antiviral mechanism

    Zhang et al. summarize the Kiwa system-level mechanism as membrane-associated phage-infection detection coordinated with effector DNA binding.

Kiwa coordinates membrane sensing with phage DNA binding

Evidence-backed process sketch linking a Kiwa kwaAB locus to KwaA-KwaB supercomplex assembly, membrane-associated phage-infection sensing, binding of ejected phage DNA, and inhibition of phage DNA replication and late transcription.

NONMECHANISTIC · The graph captures the characterized two-component Kiwa mechanism without asserting one exact phage receptor, the precise KwaA conformational change, the structural basis of KwaB DNA binding, Gam-mediated counter-defense, or RecBCD rescue as universal across all Kiwa loci.

Kiwa coordinates membrane sensing with phage DNA binding Interactive directed graph showing evidence-backed causal relationships for Kiwa system.

Edge evidence

  • Kiwa locus contributes to KwaA-KwaB supercomplex assembly RO:0002326

    The Kiwa kwaAB locus encodes KwaA and KwaB components that assemble into a membrane-associated supercomplex.

    • DOI:10.1016/j.cell.2025.07.002 KwaA and KwaB assemble into a large, membrane-associated supercomplex Zhang et al. support KwaA/KwaB supercomplex assembly.
  • KwaA-KwaB supercomplex assembly enables membrane phage sensing and DNA binding RO:0002327

    Association with KwaA is required for Kiwa antiviral activity despite independent KwaB DNA binding.

    • DOI:10.1016/j.cell.2025.07.002 its antiviral activity requires association with KwaA, suggesting spatial or conformational regulation Zhang et al. support KwaA association as required for KwaB antiviral activity.
  • membrane phage sensing and DNA binding mitigates phage replication and late transcription METPO:2007407

    KwaA sensing of phage binding coordinates with KwaB binding of ejected phage DNA to inhibit phage replication and late transcription.

    • DOI:10.1016/j.cell.2025.07.002 Upon phage binding, KwaA senses infection at the membrane, leading to KwaB binding of ejected phage DNA and inhibition of replication and late transcription Zhang et al. connect Kiwa membrane sensing and KwaB DNA binding to inhibition of phage replication and late transcription.
  • membrane phage sensing and DNA binding confers Kiwa system METPO:2007700

    Spatially coordinated membrane-associated phage sensing and effector DNA binding realizes the Kiwa antiphage-defense phenotype.

    • DOI:10.1016/j.cell.2025.07.002 Kiwa coordinates membrane-associated detection of phage infection with downstream DNA binding by its effector Zhang et al. summarize the system-level Kiwa antiviral mechanism.
  • Kiwa system is a phage defense system rdfs:subClassOf

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

    • DOI:10.1016/j.cell.2025.07.002 Our findings support a model in which Kiwa coordinates membrane-associated detection of phage infection Zhang et al. support Kiwa as an antiviral phage-defense system.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1016/j.cell.2025.07.002

Parent traits (1)

Synonyms (1)

  • Kiwa EXACT_SYNONYM · DOI:10.1016/j.cell.2025.07.002

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:10.1016/j.cell.2025.07.002 Zhang et al. characterized the Escherichia coli O55:H7 Kiwa system and showed that its KwaA/KwaB pair assembles into a membrane-associated supercomplex that inhibits phage DNA replication and late transcription.

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 Kiwa activation, phage counter-defense, and RecBCD-rescue details before minting narrower Kiwa mechanism children.

KNOWLEDGE GAP OPEN kiwa-activation-and-counterdefense-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.

Zhang et al. support a KwaA/KwaB membrane-associated antiviral supercomplex and also describe the phage Gam DNA-mimic counter-defense and RecBCD-dependent restoration of Kiwa protection, but the first TraitRecord stays at the system level until separate review resolves the activation conformational change, exact DNA-binding state, phage counter-defense breadth, and RecBCD connection.

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    Minted Kiwa 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_v108.