identifier: traitmech:000505 label: McrBC system definition: A type IV modification-dependent restriction system in which an organism possesses an mcrBC locus encoding McrB DNA-binding and McrC cleavage-associated subunits that assemble into an McrBC restriction endonuclease complex targeting methylated cytosine-containing DNA. definition_source: DOI:10.1093/emboj/20.12.3210 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000496 synonyms: - synonym_text: McrBC synonym_type: EXACT_SYNONYM source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md - synonym_text: McrBC restriction endonuclease synonym_type: RELATED_SYNONYM source: DOI:10.1093/emboj/20.12.3210 evidence: - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. notes: Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA. - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease. notes: Panne et al. support methylated-site DNA binding by McrB(L), one of the products of the E. coli K-12 mcrB gene. - reference: DOI:10.1093/emboj/20.12.3210 snippet: In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease. notes: Panne et al. support McrC as the cleavage-associated subunit of the McrBC endonuclease complex. - reference: DOI:10.1093/nar/gkt747 snippet: The rgl genes were renamed mcrA and mcrBC (modified cytosine restriction). notes: Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch that helped define Type IV restriction. - reference: DOI:10.1093/nar/gkt747 snippet: The new class of modification-dependent restriction enzymes was named Type IV, as distinct from the familiar modification-blocked Types I-III. notes: Loenen and Raleigh define the Type IV class as modification-dependent restriction enzymes. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: '| McrBC | 10\.1093/emboj/20\.12\.3210 | The McrBC restriction endonuclease assembles into a ring structure in the presence of G nucleotides | ' notes: The pinned DefenseFinder article registry maps the McrBC source key to Panne et al. canonical_examples: - taxon_id: NCBITaxon:83333 taxon_label: Escherichia coli K-12 note: Panne et al. characterized the McrBC endonuclease from Escherichia coli K-12. reference: DOI:10.1093/emboj/20.12.3210 causal_graphs: - graph_id: mcrbc_restricts_methylated_cytosine_dna title: McrBC restricts methylated-cytosine DNA description: Conservative system-level sketch linking an mcrBC locus to modification-dependent restriction of methylated-cytosine DNA and to the Type IV restriction parent trait. scope_status: NONMECHANISTIC scope_notes: The graph captures McrBC as a named, E. coli K-12-derived Type IV modification-dependent restriction system while leaving exact McrB/McrC protein activities, complete modified-cytosine target breadth, natural host breadth, and DefenseFinder RM_Type_IV HMM/rules mapping unresolved. nodes: - node_id: mcrbc_locus label: mcrBC locus node_type: GENETIC_ELEMENT description: A locus encoding the McrB and McrC subunits of the McrBC modification-dependent restriction endonuclease. - node_id: mcrbc_methylated_dna_restriction label: McrBC methylated-DNA restriction node_type: BIOLOGICAL_PROCESS description: McrBC endonuclease restriction of DNA containing modified cytosines. - node_id: mcrbc_system_trait label: McrBC system node_type: TRAIT grounding: traitmech:000505 description: Possession of a genome-encoded McrBC modification-dependent restriction system. - node_id: type_iv_modification_dependent_restriction label: type IV modification-dependent restriction system node_type: TRAIT grounding: traitmech:000496 description: Possession of a genome-encoded Type IV modification-dependent restriction system. edges: - subject: mcrbc_locus predicate: contributes to predicate_id: RO:0002326 object: mcrbc_methylated_dna_restriction description: The mcrBC locus encodes the McrBC endonuclease subunits that bind and cleave modified-cytosine DNA. evidence: - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. notes: Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA. - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease. notes: Panne et al. support methylated-site DNA binding by McrB(L), one of the products of the E. coli K-12 mcrB gene. - reference: DOI:10.1093/emboj/20.12.3210 snippet: In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease. notes: Panne et al. support McrC as the cleavage-associated subunit of the McrBC endonuclease complex. - subject: mcrbc_methylated_dna_restriction predicate: confers predicate_id: METPO:2007700 object: mcrbc_system_trait description: McrBC methylated-DNA restriction realizes the organism-level McrBC system possession trait. evidence: - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. notes: Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: '| McrBC | 10\.1093/emboj/20\.12\.3210 | The McrBC restriction endonuclease assembles into a ring structure in the presence of G nucleotides | ' notes: The pinned DefenseFinder article registry maps the McrBC source key to Panne et al. - subject: mcrbc_system_trait predicate: is a predicate_id: rdfs:subClassOf object: type_iv_modification_dependent_restriction description: McrBC system possession is a Type IV modification-dependent restriction system trait. evidence: - reference: DOI:10.1093/nar/gkt747 snippet: The rgl genes were renamed mcrA and mcrBC (modified cytosine restriction). notes: Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch that helped define Type IV restriction. - reference: DOI:10.1093/nar/gkt747 snippet: The new class of modification-dependent restriction enzymes was named Type IV, as distinct from the familiar modification-blocked Types I-III. notes: Loenen and Raleigh define the Type IV class as modification-dependent restriction enzymes. discussions: - discussion_id: mcrbc-defensefinder-model-gap prompt: Resolve exact McrB/McrC component activities, complete modified-cytosine target breadth, natural host breadth, and DefenseFinder RM_Type_IV HMM/rules mapping before minting narrower McrBC mechanism or component traits. kind: KNOWLEDGE_GAP status: OPEN rationale: Panne et al. support McrBC from Escherichia coli K-12 as a restriction endonuclease complex that cuts DNA containing modified cytosines, and Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch of Type IV modification-dependent restriction systems. The pinned DefenseFinder article registry maps the McrBC source key to Panne et al., but the pinned HMM inventory and rules table have no exact McrBC rows. This first-pass record therefore does not resolve a reusable DefenseFinder profile model, the exact relationship between individual McrB and McrC molecular functions and organism-level McrBC possession, the complete set of modified-cytosine targets, or the natural host breadth of McrBC systems. evidence: - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. notes: Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA. - reference: DOI:10.1093/emboj/20.12.3210 snippet: McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease. notes: Panne et al. support methylated-site DNA binding by McrB(L), one of the products of the E. coli K-12 mcrB gene. - reference: DOI:10.1093/emboj/20.12.3210 snippet: In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease. notes: Panne et al. support McrC as the cleavage-associated subunit of the McrBC endonuclease complex. - reference: DOI:10.1093/nar/gkt747 snippet: The rgl genes were renamed mcrA and mcrBC (modified cytosine restriction). notes: Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch that helped define Type IV restriction. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: '| McrBC | 10\.1093/emboj/20\.12\.3210 | The McrBC restriction endonuclease assembles into a ring structure in the presence of G nucleotides | ' notes: The pinned DefenseFinder article registry maps the McrBC source key to Panne et al. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md notes: A structured first-pass search of the pinned DefenseFinder HMM inventory found no exact McrBC row. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv notes: A structured first-pass search of the pinned DefenseFinder rules table found no exact McrBC system row. attaches_to: - causal_graphs#mcrbc_restricts_methylated_cytosine_dna posed_by: codex posed_date: '2026-10-01' curation_history: - timestamp: '2026-10-01T03:37:00Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted McrBC system as a DOI- and DefenseFinder-backed GENOMICS TraitRecord under the type IV modification-dependent restriction system parent 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_v382. llm_assisted: true