| AD families | AD genes | Defense system | CLAN ID | Phages/MGEs | References | Description |
|---|---|---|---|---|---|---|
| APIS003 | ArdA | restriction-modification (RM) | CLAN003 | plasmid pKM101 of E. coli | PMID:2989658 | DNA mimetics, i.e. structurally and electrostatically imitate the B-form of DNA and thus function as competitive inhibitors of restriction enzymes. |
| APIS007 | KlcA | restriction-modification (RM) | CLAN006 | IncP-1b plasmid of Bordetella pertussis | PMID:20007596 | ArdB and KlcA act as anti-restriction proteins and inhibit the four main families of Type I RM systems in vivo. |
| APIS009 | Ral | restriction-modification (RM) | CLAN008 | Lambda of E. coli | PMID:3023633 | Ral of phage λ can activate the activity of the MTase and thereby accelerate protection of the phage DNA. |
| APIS010 | Ocr | restriction-modification (RM);bacteriophage exclusion (BREX) | CLAN009 | T7 of E. coli | PMID:32338761 329108 12235377 11804597 | Ocr physically associates with BrxX methyltransferase to neutralizes their ability to both methylate and exclude incoming phage DNA. Ocr structurally mimics the DNA phosphate backbone and interacts directly with EcoKI (both the MTase and REase domain of this type I R–M enzyme), thereby interfering with the activity of this system. |
| APIS015 | IpII | restriction-modification (RM) | CLAN014 | T4 of E. coli | Silas et al., 2023 | T4 internal-protein, a T2-restricting defense system was disabled by IpII. IpII restored T2 and T6 plaquing but did not further enhance T4 infection. |
| APIS018 | Arn | restriction-modification (RM) | CLAN017 | T4 of E. coli | PMID:25118281 | T4 phage protein Arn (Anti restriction nuclease) was identified as an inhibitor of the restriction enzyme McrBC. |
| APIS021 | SieA | restriction-modification (RM) | CLAN020 | Salmonella phage P22 | Silas et al., 2023 | Superinfection exclusion. |
| APIS030 | DarB | restriction-modification (RM) | CLAN027 | P1 of E. coli | PMID:3029954 | Bind to phage DNA, thereby masking type I R–M recognition sites and preventing degradation of phage DNA. |
| APIS031 | DarA | restriction-modification (RM) | CLAN028 | P1 of E. coli | PMID:3029954 | Bind to phage DNA, thereby masking type I R–M recognition sites and preventing degradation of phage DNA. |
| APIS033 | Lar | restriction-modification (RM) | CLAN030 | Escherichia phage vB_EcoP_24B | PMID:7476171 | Lar is functionally similar to RaI, is able to alleviate restriction and enhance modification by EcoKI. And the nucleotide sequences of their genes share 47% identity, indicating a common origin. |