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)	CLAN018	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)	CLAN004	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	CLAN014	Salmonella phage S149	Silas et al., 2023	Trigger programmed cell death (PCD) by P4 prophage.
APIS009	Ral	restriction-modification (RM)	CLAN013	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)	CLAN020	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)	CLAN023	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)	CLAN022	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)	CLAN027	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)	CLAN026	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)	CLAN010	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)	CLAN019	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)	CLAN024	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)	CLAN011	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	CLAN035	Escherichia phage Mu	Silas et al., 2023	Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS020	Abc2	RecBCD	CLAN016	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)	CLAN005	Salmonella phage P22	Silas et al., 2023	Superinfection exclusion.
APIS022	adfA	toxin-antitoxin (TA)	CLAN025	RB69 of E. coli	PMID:35725776	Gene adfA(gp61.2) is encoded as a DarT (TA system) inhibitor.
APIS023	gp5.9	RecBCD	CLAN017	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	CLAN029	Salmonella phage SPFM20	Silas et al., 2023	Broad-spectrum counter-defense.
APIS030	DarB	restriction-modification (RM)	CLAN009	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)	CLAN006	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	CLAN032	Enterobacteria phage phi80	PMID:15518820	Superinfection exclusion, inactivates FhuA receptor.
APIS033	Lar	restriction-modification (RM)	CLAN007	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	CLAN036	Klebsiella phage vB_KpnM_KpV79	Silas et al., 2023	Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS035	orf148	broad-spectrum counter-defense	CLAN028	Escherichia phage OSYSP	Silas et al., 2023	Broad-spectrum counter-defense.
APIS036	gnarl3	O-antigen-based barrier	CLAN034	Escherichia phage Mangalitsa	Silas et al., 2023	Putative O-antigen modifiers, interfere with O-antigen biosynthesis.
APIS037			CLAN003
APIS039			CLAN003
APIS040			CLAN007
APIS042			CLAN005
APIS043			CLAN031	Pasteurella phage Pm86
APIS049			CLAN014
APIS059			CLAN002	Pseudoalteromonas phage HM1
APIS065			CLAN001	Shewanella sp. phage 1/4
APIS075			CLAN028	Pectobacterium phage A38
APIS077			CLAN020	Proteus phage PM 116
APIS078			CLAN023	Morganella phage vB_MmoP_MP2
APIS080			CLAN023	Klebsiella phage VLCpiA3d
APIS084			CLAN023	Pectobacterium phage phiPccP-1
APIS085			CLAN020	Escherichia phage T7
APIS086			CLAN022	Escherichia phage vB_EcoM_CE1
APIS087			CLAN020	Shigella phage ESh23
APIS090	IpI	restriction-modification (RM)	CLAN008	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)	CLAN015	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	CLAN021	Lambda of E. coli	PMID:24086157	The protein Gam inhibits the host RecBCD exonuclease activity thus allowing efficient rolling-circle replication.
APIS093			CLAN015	Pantoea phage vB_PagP-SK1
ArdB	ArdB	restriction-modification (RM)	CLAN003	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.
Stp	Stp	restriction-modification (RM)	CLAN012	T4 of E. coli	PMID:7791212	Stp has been implicated with activation of the anticodon nuclease and inhibition of EcoprrI restriction.