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McrBC system

traitmech:000505 · CLASS · PROPOSED

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.

Trait evidence (6)

  • DOI:10.1093/emboj/20.12.3210
    McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines.

    Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA.

  • DOI:10.1093/emboj/20.12.3210
    McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease.

    Panne et al. support methylated-site DNA binding by McrB(L), one of the products of the E. coli K-12 mcrB gene.

  • DOI:10.1093/emboj/20.12.3210
    In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease.

    Panne et al. support McrC as the cleavage-associated subunit of the McrBC endonuclease complex.

  • DOI:10.1093/nar/gkt747
    The rgl genes were renamed mcrA and mcrBC (modified cytosine restriction).

    Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch that helped define Type IV restriction.

  • DOI:10.1093/nar/gkt747
    The new class of modification-dependent restriction enzymes was named Type IV, as distinct from the familiar modification-blocked Types I-III.

    Loenen and Raleigh define the Type IV class as modification-dependent restriction enzymes.

  • https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
    | McrBC | 10\.1093/emboj/20\.12\.3210 | The McrBC restriction endonuclease assembles into a ring structure in the presence of G nucleotides |

    The pinned DefenseFinder article registry maps the McrBC source key to Panne et al.

McrBC restricts methylated-cytosine DNA

Conservative system-level sketch linking an mcrBC locus to modification-dependent restriction of methylated-cytosine DNA and to the Type IV restriction parent trait.

NONMECHANISTIC · 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.

McrBC restricts methylated-cytosine DNA Interactive directed graph showing evidence-backed causal relationships for McrBC system.

Edge evidence

  • mcrBC locus contributes to McrBC methylated-DNA restriction RO:0002326

    The mcrBC locus encodes the McrBC endonuclease subunits that bind and cleave modified-cytosine DNA.

    • DOI:10.1093/emboj/20.12.3210 McrBC from Escherichia coli K-12 is a restriction enzyme that belongs to the family of AAA(+) proteins and cuts DNA containing modified cytosines. Panne et al. identify McrBC from Escherichia coli K-12 as a restriction enzyme that attacks modified-cytosine DNA.
    • DOI:10.1093/emboj/20.12.3210 McrB(L) binds specifically to the methylated recognition site and is, therefore, the DNA-binding moiety of the McrBC endonuclease. Panne et al. support methylated-site DNA binding by McrB(L), one of the products of the E. coli K-12 mcrB gene.
    • DOI:10.1093/emboj/20.12.3210 In the presence of McrC, a subunit that is essential for DNA cleavage, the tetradecameric species was the major form of the endonuclease. Panne et al. support McrC as the cleavage-associated subunit of the McrBC endonuclease complex.
  • McrBC methylated-DNA restriction confers McrBC system METPO:2007700

    McrBC methylated-DNA restriction realizes the organism-level McrBC system possession trait.

  • McrBC system is a type IV modification-dependent restriction system rdfs:subClassOf

    McrBC system possession is a Type IV modification-dependent restriction system trait.

    • DOI:10.1093/nar/gkt747 The rgl genes were renamed mcrA and mcrBC (modified cytosine restriction). Loenen and Raleigh place mcrBC in the modified-cytosine restriction branch that helped define Type IV restriction.
    • DOI:10.1093/nar/gkt747 The new class of modification-dependent restriction enzymes was named Type IV, as distinct from the familiar modification-blocked Types I-III. Loenen and Raleigh define the Type IV class as modification-dependent restriction enzymes.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1093/emboj/20.12.3210

Parent traits (1)

Synonyms (2)

  • McrBC EXACT_SYNONYM · https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md
  • McrBC restriction endonuclease RELATED_SYNONYM · DOI:10.1093/emboj/20.12.3210

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.

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 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.

KNOWLEDGE GAP OPEN mcrbc-defensefinder-model-gap · raised by codex · 2026-10-01

Attached to causal_graphs#mcrbc_restricts_methylated_cytosine_dna

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

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    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.