identifier: traitmech:000363
label: Lit system
definition: A phage defense system in which an organism possesses a Lit locus represented
  by DefenseFinder as a single-profile model requiring Lit__Lit.
definition_source: DOI:10.1021/bi0495026
trait_category: GENOMICS
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- traitmech:000209
synonyms:
- synonym_text: Lit
  synonym_type: RELATED_SYNONYM
  source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
- synonym_text: Gol-Lit
  synonym_type: RELATED_SYNONYM
  source: PMID:21129205
- synonym_text: Lit__Lit
  synonym_type: RELATED_SYNONYM
  source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
evidence:
- reference: PMID:15196039
  snippet: Bacteriophage exclusion is a suicide response to viral infection. In strains
    of Escherichia coli K-12 infected with T4 phage this process is mediated by the
    host-encoded Lit peptidase. Lit is activated by a unique sequence in the major
    head protein of the T4 phage (the Gol sequence) which then cleaves site-specifically
    the host translation factor EF-Tu, ultimately leading to cell death.
  notes: Copeland et al. support host Lit as a T4-activated bacteriophage-exclusion
    peptidase that cleaves EF-Tu and leads to cell death.
- reference: PMID:21129205
  snippet: phage exclusion systems that involve T4-mediated activation of a latent
    endoribonuclease (PrrC) and cofactor-assisted activation of EF-Tu proteolysis
    (Gol-Lit)
  notes: Uzan et al. name Gol-Lit as a T4 phage-exclusion system whose output is cofactor-assisted
    activation of EF-Tu proteolysis.
- reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
  snippet: 'Lit | 10\.1186/1743-422X-7-360 | Post-transcriptional control by bacteriophage
    T4: mRNA decay and inhibition of translation initiation'
  notes: The DefenseFinder article registry maps the named Lit system to the Uzan
    et al. T4 post-transcriptional-control review.
- reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv
  snippet: "Lit\tLit\t1\t1\tLit__Lit"
  notes: The DefenseFinder rules table models Lit as a single-mandatory-profile system
    with the Lit__Lit profile.
- reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
  snippet: '| Lit__Lit                                         | Lit__Lit                                         |
    Lit                    | Custom                  | 20     |'
  notes: The DefenseFinder HMM inventory records Lit__Lit under Lit.
causal_graphs:
- graph_id: lit_locus_restricts_t4_phage
  title: Lit loci confer T4 phage exclusion
  description: Conservative system-level sketch linking possession of a Lit locus
    to T4 Gol-Lit phage exclusion without asserting a protein-resolved Lit mechanism
    node.
  scope_status: NONMECHANISTIC
  scope_notes: The graph captures Lit as a named DefenseFinder single-profile phage-exclusion
    system while leaving natural host breadth, non-e14 Lit loci, and the exact DefenseFinder
    profile-to-activity mapping unresolved.
  nodes:
  - node_id: lit_locus
    label: Lit locus
    node_type: GENETIC_ELEMENT
    description: A DefenseFinder Lit phage-defense locus represented by the Lit__Lit
      profile.
  - node_id: t4_gol_lit_phage_exclusion
    label: T4 Gol-Lit phage exclusion
    node_type: BIOLOGICAL_PROCESS
    description: Bacteriophage T4 exclusion mediated by Gol-activated Lit proteolysis
      of the host translation factor EF-Tu.
  - node_id: lit_system_trait
    label: Lit system
    node_type: TRAIT
    grounding: traitmech:000363
    description: Possession of a genome-encoded Lit phage-defense system.
  - node_id: phage_defense_system
    label: phage defense system
    node_type: TRAIT
    grounding: traitmech:000209
    description: Possession of one or more genome-encoded immune systems that inhibit
      bacteriophage infection.
  edges:
  - subject: lit_locus
    predicate: contributes to
    predicate_id: RO:0002326
    object: t4_gol_lit_phage_exclusion
    description: Lit phage-defense loci can mediate T4 bacteriophage exclusion through
      Gol-activated EF-Tu proteolysis, and DefenseFinder models Lit as a single-profile
      system.
    evidence:
    - reference: PMID:15196039
      snippet: Bacteriophage exclusion is a suicide response to viral infection. In
        strains of Escherichia coli K-12 infected with T4 phage this process is mediated
        by the host-encoded Lit peptidase. Lit is activated by a unique sequence in
        the major head protein of the T4 phage (the Gol sequence) which then cleaves
        site-specifically the host translation factor EF-Tu, ultimately leading to
        cell death.
      notes: Copeland et al. support Lit-mediated bacteriophage exclusion and EF-Tu
        cleavage.
    - reference: PMID:21129205
      snippet: phage exclusion systems that involve T4-mediated activation of a latent
        endoribonuclease (PrrC) and cofactor-assisted activation of EF-Tu proteolysis
        (Gol-Lit)
      notes: Uzan et al. identify Gol-Lit as a phage-exclusion system mediated by
        EF-Tu proteolysis.
    - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
      snippet: 'Lit | 10\.1186/1743-422X-7-360 | Post-transcriptional control by bacteriophage
        T4: mRNA decay and inhibition of translation initiation'
      notes: The DefenseFinder article registry maps the named Lit system to the Uzan
        et al. T4 post-transcriptional-control review.
    - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv
      snippet: "Lit\tLit\t1\t1\tLit__Lit"
      notes: The DefenseFinder rules table models Lit as a single-mandatory-profile
        system with the Lit__Lit profile.
    - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md
      snippet: '| Lit__Lit                                         | Lit__Lit                                         |
        Lit                    | Custom                  | 20     |'
      notes: The DefenseFinder HMM inventory records Lit__Lit under Lit.
  - subject: t4_gol_lit_phage_exclusion
    predicate: confers
    predicate_id: METPO:2007700
    object: lit_system_trait
    description: T4 Gol-Lit phage exclusion realizes the Lit system trait.
    evidence:
    - reference: PMID:15196039
      snippet: Bacteriophage exclusion is a suicide response to viral infection. In
        strains of Escherichia coli K-12 infected with T4 phage this process is mediated
        by the host-encoded Lit peptidase. Lit is activated by a unique sequence in
        the major head protein of the T4 phage (the Gol sequence) which then cleaves
        site-specifically the host translation factor EF-Tu, ultimately leading to
        cell death.
      notes: Copeland et al. connect host-encoded Lit to T4 bacteriophage exclusion.
  - subject: lit_system_trait
    predicate: is a
    predicate_id: rdfs:subClassOf
    object: phage_defense_system
    description: Lit system possession is a phage-defense-system trait.
    evidence:
    - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
      snippet: 'Lit | 10\.1186/1743-422X-7-360 | Post-transcriptional control by bacteriophage
        T4: mRNA decay and inhibition of translation initiation'
      notes: The DefenseFinder article registry maps the named Lit system to the Uzan
        et al. T4 post-transcriptional-control review.
    - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv
      snippet: "Lit\tLit\t1\t1\tLit__Lit"
      notes: The DefenseFinder rules table models Lit as a single-mandatory-profile
        system with the Lit__Lit profile.
discussions:
- discussion_id: lit-mechanism-gap
  prompt: Resolve natural Lit loci, host breadth beyond Escherichia coli K-12 e14,
    Gol-activation contexts, and Lit__Lit profile-to-activity mapping before minting
    narrower Lit mechanism children.
  kind: KNOWLEDGE_GAP
  status: OPEN
  rationale: Copeland et al. support the T4-triggered e14 Lit peptidase as a bacteriophage-exclusion
    determinant, Uzan et al. summarize Gol-Lit as a T4 phage-exclusion system, and
    DefenseFinder models Lit as a single-profile system. The natural host breadth
    and profile-to-activity mapping remain unresolved.
  attaches_to:
  - causal_graphs#lit_locus_restricts_t4_phage
  posed_by: codex
  posed_date: '2026-09-22'
curation_history:
- timestamp: '2026-09-22T10:38:17Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Minted Lit system as a DOI-backed GENOMICS TraitRecord under phage defense
    system after an ignored-and-hidden duplicate review found no exact live TraitMech,
    METPO, history, or prior proposal record; the replacement placeholder is reserved
    in proposals/metpo_traitmech_v240.
  llm_assisted: true