Browse anti-prokaryotic immune system families by Host order

AD families AD genes Defense system CLAN ID Phages/MGEs References Description
APIS002 vs.4 cyclic oligonucleotide-based antiphage signaling system (CBASS) CLAN056 T4 of E. coli PMID:36848932 Vs.4 antagonized cGAS signaling by binding tightly to cGAMP (dissociation constant of approximately 30 nM) and sequestering it; Bioinformatic analyses identified 198 homologues of Vs.4 in diverse phages; belongs to PHROG 717.
APIS003 ArdA restriction-modification (RM) CLAN005 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.
APIS006 abc1 RecBCD CLAN037 Salmonella phage S149 Silas et al., 2023 Trigger programmed cell death (PCD) by P4 prophage.
APIS009 Ral restriction-modification (RM) CLAN057 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) CLAN017 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.
APIS011 gp4.5 toxin-antitoxin (TA) CLAN024 T7 of E. coli PMID:23478446 Protein gp4.5 allows T7 to block Lon (protease) from degrading antitoxins (the SanTA system in E. coli), including SanaA, thereby preventing liberation of SanaT. However, beyond a possible interaction between gp4.5 and Lon in uninfected cells, this speculative model remains untested.
APIS012 tifA toxin-antitoxin (TA) CLAN038 T4 of E. coli PMID:35924892 Original gene 61.4, experimentally evolved T4 phage to overcome a phage-defensive toxin-antitoxin system (toxIN) in E. coli. Through recombination, T4 rapidly acquires segmental amplifications of a previously uncharacterized gene, now named tifA, encoding an inhibitor of the toxin, ToxN.
APIS013 Dmd toxin-antitoxin (TA) CLAN058 T4 of E. coli PMID:22403819 T4 produces Dmd, an antitoxin that inhibits E. coli RnlA and LsoA toxins. Dmd differs from the RnlB or LsoB antitoxins, suggesting it evolved independently, which is highlighted by its different toxin neutralization mechanism.
APIS014 PinA toxin-antitoxin (TA) CLAN059 T4 of E. coli PMID:9417110 PinA encoded by T4 was discovered 20 years ago, it could help T4 block TA defense systems that require Lon, but in vivo function for pinA has not been reported.
APIS015 IpII restriction-modification (RM) CLAN060 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.
APIS016 Acb1 cyclic oligonucleotide-based antiphage signaling system (CBASS) CLAN061 T4 of E. coli PMID:35395152 Acb1 rapidly degrades the CBASS signals 3′3′-cGAMP, cUA and cAAA, but does not cleave cGG.
APIS017 Alt toxin-antitoxin (TA) CLAN062 T4 of E. coli PMID:26395283 T4 protein Alt (an ADP-ribosyltransferase) is injected with phage DNA, which chemically modifies the MazF toxin. ADP-ribosylated MazF has reduced cleavage activity, enabling the survival of the phage.
APIS018 Arn restriction-modification (RM) CLAN063 T4 of E. coli PMID:25118281 T4 phage protein Arn (Anti restriction nuclease) was identified as an inhibitor of the restriction enzyme McrBC.
APIS019 gnarl2 O-antigen-based barrier CLAN064 Escherichia phage Mu Silas et al., 2023 Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS020 Abc2 RecBCD CLAN065 Salmonella phage P22 PMID:10669596 36533901 Bacteriophage P22 Abc2 protein binds to the RecBCD enzyme from E. coli to promote phage growth and recombination; the RecBCD-Abc2 structure shows that Abc2 binds to the Chi-recognition domains of the RecC subunit in a position that might enable it to mediate the loading of phage recombinases onto its single-stranded DNA products.
APIS021 SieA restriction-modification (RM) CLAN039 Salmonella phage P22 Silas et al., 2023 Superinfection exclusion.
APIS022 adfA toxin-antitoxin (TA) CLAN066 RB69 of E. coli PMID:35725776 Gene adfA(gp61.2) is encoded as a DarT (TA system) inhibitor.
APIS023 gp5.9 RecBCD CLAN067 T7 of E. coli PMID:36533901 Gp5.9 completely inhibits RecBCD by preventing it from binding to DNA. The RecBCD-gp5.9 structure shows that gp5.9 acts by substrate mimicry, binding predominantly to the RecB arm domain and competing sterically for the DNA binding site.
APIS026 orf126 broad-spectrum counter-defense CLAN069 Salmonella phage SPFM20 Silas et al., 2023 Broad-spectrum counter-defense.
APIS030 DarB restriction-modification (RM) CLAN071 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) CLAN040 P1 of E. coli PMID:3029954 Bind to phage DNA, thereby masking type I R–M recognition sites and preventing degradation of phage DNA.
APIS032 Cor superinfection exclusion CLAN072 Enterobacteria phage phi80 PMID:15518820 Superinfection exclusion, inactivates FhuA receptor.
APIS033 Lar restriction-modification (RM) CLAN041 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.
APIS034 gnarl1 O-antigen-based barrier CLAN073 Klebsiella phage vB_KpnM_KpV79 Silas et al., 2023 Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS035 orf148 broad-spectrum counter-defense CLAN018 Escherichia phage OSYSP Silas et al., 2023 Broad-spectrum counter-defense.
APIS036 gnarl3 O-antigen-based barrier CLAN074 Escherichia phage Mangalitsa Silas et al., 2023 Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS037 CLAN011
APIS039 CLAN011
APIS040 CLAN041
APIS042 CLAN039
APIS043 CLAN001 Pasteurella phage Pm86
APIS049 CLAN037
APIS059 CLAN023 Pseudoalteromonas phage HM1
APIS065 CLAN009 Shewanella sp. phage 1/4
APIS075 CLAN018 Pectobacterium phage A38
APIS077 CLAN017 Proteus phage PM 116
APIS078 CLAN024 Morganella phage vB_MmoP_MP2
APIS080 CLAN024 Klebsiella phage VLCpiA3d
APIS084 CLAN024 Pectobacterium phage phiPccP-1
APIS085 CLAN017 Escherichia phage T7
APIS086 CLAN038 Escherichia phage vB_EcoM_CE1
APIS087 CLAN017 Shigella phage ESh23
APIS090 IpI restriction-modification (RM) CLAN075 T4 of E. coli PMID:17188297 18037438 Restriction endonuclease inhibitor IpI blocks the ancestral two-component type IV R-M system and represents a third generation bacteriophage defense against restriction nucleases of the Gmr type.
APIS091 HOS17_gp01 restriction-modification (RM);bacteriophage exclusion (BREX) CLAN042 T3 of E. coli Andriianov et al., 2023 T3 encodes a SAMase that circumvents the SAM-dependent Type I R-M defence of the host E. coli through cleavage of S-adenosyl-methionine (SAM). SAMase also allows T3 to evade BREX defence.
APIS092 Gam RecBCD CLAN076 Lambda of E. coli PMID:24086157 The protein Gam inhibits the host RecBCD exonuclease activity thus allowing efficient rolling-circle replication.
APIS093 CLAN042 Pantoea phage vB_PagP-SK1
APIS094 Rad Retron CLAN025 Escherichia phage SP15 Azam et al., 2023 Rad inhibited retron function by degrading noncoding RNA, the precursor of msDNA.
APIS100 CLAN011
APIS103 NTases CBASS,Pycsar,CRISPR–Cas (type III) CLAN010 Bacillus phage BCP1 PMID:36952342 A family of bacteriophage nucleotidyltransferases (NTases) that synthesize competitor cyclic dinucleotide (CDN) ligands and inhibit TIR NADase effectors activated via a linked STING CDN sensor domain (TIR-STING). 
APIS106 CLAN019
APIS107 dam restriction-modification (RM) CLAN026 Escherichia phage T4 PMID:6307815 DNA adenine methylases methylate adenine residues in specific sequences, the methylation site of the host Escherichia coli dam+ methylase. Methylation protects the site against cleavage by the MboI restriction nuclease.
APIS108 ardc restriction-modification (RM) CLAN078 Enterobacterales PMID:10686096 This anti-restriction protein is able in vitro to protect the single-stranded DNA against the activity of type II restriction endonuclease HhaI.
APIS111 mom restriction-modification (RM) CLAN079 Escherichia phage Mu PMID:2934296 Methylcarbamoylase for DNA modification.
APIS117 mga47 toxin-antitoxin (TA) CLAN080 Escherichia phage SECphi18 PMID:35725776 DNA polymerase
APIS119 Ulx restriction-modification (RM) CLAN081 Escherichia phage P1 PMID:28509398 Ulx is a protein included in the P1 antirestriction system. It acts as a chaperone or packaging factor to increase the amount of DarB incorporated into the virion.
APIS124 CLAN030
APIS125 U56 toxin-antitoxin (TA) CLAN045 Escherichia phage Ukendt PMID:38788717 Retron-Eco1 inhibitor
APIS129 Lidtsur-6 AVAST (Antiviral STAND) CLAN031 Escherichia phage Lidtsur PMID:35951700 Lidtsur-6, Lidtsur-17 and Forsur-7 were active in phage plaque assays and restored phage propagation on Avs-containing E. coli.
APIS130 RacC Retron CLAN082 prophage of Escherichia coli str. K-12 substr. MG1655 PMID:35850148 RacC is a Rac prophage gene, function as retron TA blocker. It directly blocks RcaT toxicity, inhibit the toxin of abortive infection systems.
APIS135 CLAN030
APIS138 CLAN027
APIS140 CLAN031
APIS141 CLAN020
APIS143 Hdf restriction-modification (RM) CLAN030 Escherichia phage P1 PMID:28509398 A key member in the P1 Dar antirestriction system. The absence of either Hdf or DarA results in failure to incorporate any of the other antirestriction proteins.
APIS145 CLAN027
APIS152 dmt restriction-modification (RM) CLAN026 Escherichia phage P1 PMID:14715260 DNA methyltransferase (M.EcoP1I) encoded by prophage P1, may protect the phage genome from restriction by type III restriction enzymes and thus could be considered as an anti-restriction system.
APIS157 CLAN004
APIS160 narp1_adps NAD+ reconstitution pathway (NARP) CLAN027 Escherichia phage JohannRWettstein Osterman et al., 2024 Phage enzyme ADPR-PP synthetase (Adps).
APIS161 CLAN026
APIS164 Lidtsur-17 AVAST (Antiviral STAND) CLAN087 Escherichia phage Lidtsur PMID:35951700 Lidtsur-17 inhibits SeAvs3 nuclease activity in vitro.
APIS165 Ddra restriction-modification (RM) CLAN088 Escherichia phage P1 PMID:28509398 It's included in the P1 restriction system. The proteins Hdf, DarA and DdrA are required for the protection of phage DNA from restriction by the EcoA Type I R-M system.
APIS179 Ddrb restriction-modification (RM) CLAN089 Escherichia phage P1 PMID:28509398 It's included in the P1 restriction system. The presence of DdrB results in reduced antirestriction activity, presumably by negatively affecting DarB but the mechanism is not known.
APIS180 psib SOS response CLAN090 Escherichia coli PMID:19818715 PsiB protein works as an SOS inhibitor that binds to RecA to inhibit its activities.
APIS193 Forsur-7 AVAST (Antiviral STAND) CLAN031 Escherichia phage forsur PMID:35951700 Forsur-7 inhibits SeAvs3 nuclease activity in vitro to a lesser degree.
APIS195 AdfN toxin-antitoxin (TA) CLAN091 Escherichia phage T4 PMID:39026772 Anti-DarT factor NADAR (AdfN), removes ADP-ribose modifications from phage DNA during infection thereby enabling replication in DarTG1-containing bacteria. AdfN, like DarG1, is in the NADAR superfamily of ADP-ribosylglycohydrolases.
APIS197 narp1_namat NAD+ reconstitution pathway (NARP) CLAN043 Escherichia phage JohannRWettstein Osterman et al., 2024 Phage enzyme Nicotinamide ADPR-transferase (Namat)
ArdB ArdB restriction-modification (RM) CLAN011 plasmid pKM101 of E. coli PMID:8393008 Like ArdA, ArdB efficiently inhibits restriction by members of the three known families of type I systems of E. coli and only slightly affects the type II enzyme, EcoRI.
psia psia SOS response CLAN117 Enterobacteriaceae Samuel and Burstein, 2023 SOS-inhibitor.
Stp Stp restriction-modification (RM) CLAN107 T4 of E. coli PMID:7791212 Stp has been implicated with activation of the anticodon nuclease and inhibition of EcoprrI restriction.
APIS276 T7K Retron-Eco9,DarTG1 CLAN017 Escherichia phage T7 Bartolec et al., 2024 The T7 kinase weakens the activity of phage defense systems by phosphorylation, and is likely a broadly-acting phage counter-defense system.
APIS287 Acb5A Type I CBASS CLAN002 PMID:41785351 cleaves cyclic guanosine monophosphate–adenosine monosphosphate (3′3′-cGaMP) and related molecules
APIS204 dpda restriction-modification (RM) CLAN028 Escherichia phage CAjan PMID:31784519 In Enterobacteria phage 9g, dpdA is associated with G+ synthesis. This modification is proposed to play an anti-restriction role because 7-deazaguanine derivatives can block the activity of a wide variety of restriction enzymes
APIS281 fole restriction-modification (RM) CLAN035 Enterobacteria phage 9g PMID:31784519 Enzyme to synthesize deazaguanines in G+ synthesis for anti-RM
APIS294 qued restriction-modification (RM) CLAN049 Enterobacteria phage 9g PMID:31784519 Enzyme to synthesize deazaguanines in G+ synthesis for anti-RM
APIS363 quee restriction-modification (RM) CLAN103 Enterobacteria phage 9g PMID:31784519 Enzyme to synthesize deazaguanines in G+ synthesis for anti-RM
APIS276 jss1_004 Dnd,QatABCD,SIR2+HerA,DUF4297+HerA,CRISPR‒Cas CLAN017 Salmonella phage JSS1 PMID:39506096 JSS1_004 employs N-terminal Ser/Thr/Tyr protein kinase activity to catalyse the multisite phosphorylation of host DndFGH. It also phosphorylates other bacterial immune systems to varying degrees, including CRISPR‒Cas, QatABCD, SIR2+HerA and DUF4297+HerA.
APIS355 T5.014 bNACHT CLAN102 Escherichia phage T5 PMID:37160116 The gene orf015 (T5.014) alter the activity of a wide variety of bNACHT genes and provide evidence for a complicated relationship between phage genes and bNACHT-based host defense systems, where orf008 activates and orf015 inhibits bNACHT proteins.
APIS244 orf72 BREX type I CLAN050 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF72 has anti-Brex type I activity, was predicted to be a Plasmid replication region DNA-binding N-term
APIS307 orf65 hhe CLAN099 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF65 shows anti-hhe activity, predicted as a transcriptional regulator protein (SplA).
APIS312 orf55 AVAST type III CLAN022 Escherichia phage Dru_SM1 Ojima et al., 2024 It has anti-AVAST type III activity, was predicted to be a ATP-dependent DNA ligase.
APIS325 orf46 BREX type I CLAN101 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF46 exhibits anti-Brex type I activity, as a trimethylamine methyltransferase corrinoid protein.
APIS345 orf58 Sir2-HerA,DUF4297-HerA CLAN032 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF58 has anti-SIR2+HerA and DUF4297+HerA activity as well as Reron Ec86 sensor activity, was predicted to be a “Mu-like prophage host-nuclease inhibitor protein Gam
APIS354 orf83 AVAST type III CLAN012 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF83 exhibits anti-AVAST type III activity, was predicted to be a “nucleotide-binding protein DprA/Smf involved in DNA uptake”.
Druad1 Druad1 Druantia type I CLAN106 Escherichia phage Dru_SM1 Ojima et al., 2024 ORF71 exhibits anti-Druantia type I activity, was predicted to belong to a family of unknown function (DUF6614).
APIS308 orf35 Tmn CLAN100 Escherichia phage SM_S22 PMID:39987292 Deletion of ORF35 from the ΦSMS22 genome resulted in reduced infectivity against E. coli expressing Tmn, suggesting that ORF35 functions as an anti-Tmn
APIS369 acb3 type III CBASS CLAN007 PMID:39855193 Acb3 encodes a conserved loop that is predicted to block the active site of CD-NTases and interact with the nucleotidyltransferase catalytic residues via hydrogen and ionic bonds. 
APIS279 T5Dmp Kongming CLAN021 Escherichia phage T5 PMID:39977546 A deoxyribonucleoside 5′-monophosphatase functions as an anti-Kongming factor.
APIS279 bas26_0202 Kongming CLAN021 Escherichia phage GreteKellenberger PMID:39977546 The protein robustly suppressed cell death triggered by Kongming and their respective DNKs, indicating anti-Kongming function.