Description
AVAST (antiviral ATPases/NTPases of the STAND superfamily) is a group of anti-phage defense systems, active against some dsDNA phages.
AVAST systems are composed of NTPases of the STAND (signal transduction ATPases with numerous associated domains) superfamily (1). STAND-NTPases typically contain a C-terminal helical sensor domain that activates the N-terminal effector domain upon target recognition (1).
In eukaryotes, STAND-NTPases are associated with programmed cell death, therefore Gao and colleagues hypothesized that AVAST might function through an Abortive infection mechanism.
Example of genomic structure
The AVAST system have been describe in a total of 5 subsystems.
Here is some example found in the RefSeq database:
AVAST_I subsystem in the genome of Vibrio sp. (GCF_905175355.1) is composed of 3 proteins: Avs1A (WP_208445041.1), Avs1B (WP_208445042.1)and, Avs1C (WP_108173272.1).
AVAST_II subsystem in the genome of Escherichia coli (GCF_018884505.1) is composed of 1 protein: Avs2A (WP_032199984.1).
AVAST_III subsystem in the genome of Enterobacter cancerogenus (GCF_002850575.1) is composed of 2 proteins: Avs3B (WP_199559884.1)and, Avs3A (WP_101737373.1).
AVAST_IV subsystem in the genome of Escherichia coli (GCF_016903595.1) is composed of 1 protein: Avs4A (WP_000240574.1).
AVAST_V subsystem in the genome of Leclercia adecarboxylata (GCF_006171285.1) is composed of 1 protein: Avs5A (WP_139565349.1).
Distribution of the system among prokaryotes
The AVAST system is present in a total of 363 different species.
Among the 22k complete genomes of RefSeq, this system is present in 1046 genomes (4.6 %).
Proportion of genome encoding the AVAST system for the 14 phyla with more than 50 genomes in the RefSeq database. Pie chart of the repartition of all the subsystems found in the RefSeq database.
Experimental validation
AVAST systems were experimentally validated using:
Subsystem SIR2-STAND with a system from Escherichia fergusonii's PICI (EfCIRHB19-C05) in Escherichia coli has an anti-phage effect against T4, Lambda, HK97, HK544, HK578, T7 (Fillol-Salom et al., 2022)
Subsystem SIR2-STAND with a system from Escherichia fergusonii's PICI (EfCIRHB19-C05) in *Salmonella enterica * has an anti-phage effect against P22, BTP1, ES18, det7 (Fillol-Salom et al., 2022)
Subsystem SIR2-STAND with a system from Escherichia fergusonii's PICI (EfCIRHB19-C05) in *Klebsiella pneumoniae * has an anti-phage effect against Pokey (Fillol-Salom et al., 2022)
Subsystem Metallo beta-lactamase + protease + STAND (Type 1) with a system from Erwinia piriflorinigrans in Escherichia coli has an anti-phage effect against P1 (Gao et al., 2020)
Subsystem STAND (Type 2) with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T4, P1 (Gao et al., 2020)
Subsystem DUF4297-STAND (Type 3) with a system from Salmonella enterica in Escherichia coli has an anti-phage effect against T2, T3, T7, PhiV-1 (Gao et al., 2020)
Subsystem Mrr-STAND (Type 4) with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T3, T7, PhiV-1 (Gao et al., 2020)
Subsystem SIR2-STAND (Type 5) with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T2 (Gao et al., 2020)
Subsystem SeAvs1 with a system from Salmonella enterica in Escherichia coli has an anti-phage effect against P1, ZL-19 (Gao et al., 2022)
Subsystem EcAcs1 with a system from Escherichia coli in Escherichia coli has an anti-phage effect against ZL-19 (Gao et al., 2022)
Subsystem EpAvs1 with a system from Erwinia piriflorinigrans in Escherichia coli has an anti-phage effect against P1, Lambda, , ZL-19 (Gao et al., 2022)
Subsystem SeAvs3 with a system from Salmonella enterica in Escherichia coli has an anti-phage effect against T7, PhiV-1, ZL-19 (Gao et al., 2022)
Subsystem KvAvs3 with a system from Klebsiella variicola in Escherichia coli has an anti-phage effect against P1, ZL-19 (Gao et al., 2022)
Subsystem EcAvs2 with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T7, PhiV-1, P1, T4, T5, ZL-19 (Gao et al., 2022)
Subsystem Ec2Avs2 with a system from Escherichia coli in Escherichia coli has an anti-phage effect against P1 (Gao et al., 2022)
Subsystem EcAvs4 with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T7, PhiV-1, ZL-19 (Gao et al., 2022)
Subsystem Ec2Avs4 with a system from Escherichia coli in Escherichia coli has an anti-phage effect against T7, PhiV-1, ZL-19 (Gao et al., 2022)
Subsystem KpAvs4 with a system from Klebsiella pneumoniae in Escherichia coli has an anti-phage effect against ZL-19 (Gao et al., 2022)
Subsystem CcAvs4 with a system from Corallococcus coralloides in Escherichia coli has an anti-phage effect against T7 (Gao et al., 2022)