Gene Ontology annotation through association of InterPro records with GO terms.

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

Two DNA antirestriction systems of bacteriophage P1, darA, and darB - characterization of darA- phages

The multicomponent antirestriction system of phage P1 is linked to capsid morphogenesis

Reassembling a cannon in the DNA defense arsenal: Genetics of StySA, a BREX phage exclusion system in Salmonella lab strains.

Injected DarB carries a bioinformatic signature of methyltransferase, but how it acts against diverse restriction-modification systems remains unresolved; catalytic activity has not been directly demonstrated.

PMID:38989624

Ocr-mediated suppression of BrxX unveils a phage counter-defense mechanism.

Contemporary phage-counter-defense work (Ocr inhibits the BREX methyltransferase BrxX as a DNA mimic) provides an experimental template for assaying SAM-dependent methyltransferases - DNA Km approximately 3.4 uM, SAM Km approximately 380 uM, Ocr IC50 approximately 1.17 uM - relevant for future biochemical validation of DarB methyltransferase predictions.

PMID:29228259

The non-specific adenine DNA methyltransferase M.EcoGII.

A representative adenine DNA methyltransferase (M.EcoGII) installs N6-methyladenine using SAM and contains hallmark SAM-dependent MTase motifs (FxGxG AdoMet-binding motif and DPPY catalytic motif); supports the family-level inference that DarB-like proteins, given their predicted SAM-dependent MTase domain, could perform similar chemistry.

PMID:40856689

Biology of host-dependent restriction-modification in prokaryotes.

The P1 dar system (DarA, DarB, Ulx, DdrB, DdrA, Hdf) is virion-head-incorporated and confers protection against several Type I HDRM systems and BREX, acting only in cis on DNA packaged within the virion, supporting a model of physical obstruction of host restriction machinery.

doi:10.52601/bpr.2025.240070

Bacterial restriction-modification systems: mechanisms of defense against phage infection

DarA/DarB are described as co-injected proteins that occlude restriction sites on the P1 genome to avoid destruction by host RM systems; the cis-only behaviour is consistent with restriction-site shielding rather than diffusible enzymatic activity.

file:9CAUD/darB/darB-deep-research-falcon.md

Deep research report on darB/Q9XJG2 (Falcon/Edison Scientific Literature)

No primary publication directly characterizes UniProt Q9XJG2 (Punavirus P1 darB'); the prevailing literature treats DarB as a virion-delivered anti-restriction factor with a bioinformatic methyltransferase signature but no biochemically validated methyltransferase activity.
Best-supported mode of action for the P1 Dar system is protein-mediated physical obstruction (restriction-site shielding) acting in cis on virion-packaged DNA against several Type I HDRM systems and BREX; methyltransferase chemistry, if any, remains a domain-level inference.
Critical experimental gaps for Q9XJG2 are direct methyltransferase activity assay, identification of the modified base (m6A/m4C/m5C), recognition motif and specificity, and confirmation that the UniProt fragment is catalytically competent.