PMID:17158670

Citation	Dziewit, L, Jazurek, M, Drewniak, L, Baj, J and Bartosik, D (2007) The SXT conjugative element and linear prophage N15 encode toxin-antitoxin-stabilizing systems homologous to the tad-ata module of the Paracoccus aminophilus plasmid pAMI2. J. Bacteriol. 189:1983-97
Abstract	A group of proteic toxin-antitoxin (TA) cassettes whose representatives are widely distributed among bacterial genomes has been identified. These cassettes occur in chromosomes, plasmids, bacteriophages, and noncomposite transposons, as well as in the SXT conjugative element of Vibrio cholerae. The following four homologous loci were subjected to detailed comparative studies: (i) tad-ata from plasmid pAMI2 of Paracoccus aminophilus (the prototype of this group), (ii) gp49-gp48 from the linear bacteriophage N15 of Escherichia coli, (iii) s045-s044 from SXT, and (iv) Z3230-Z3231 from the genomic island of enterohemorrhagic Escherichia coli O157:H7 strain EDL933. Functional analysis revealed that all but one of these loci (Z3230-Z3231) are able to stabilize heterologous replicons, although the host ranges varied. The TA cassettes analyzed have the following common features: (i) the toxins are encoded by the first gene of each operon; (ii) the antitoxins contain a predicted helix-turn-helix motif of the XRE family; and (iii) the cassettes have two promoters that are different strengths, one which is located upstream of the toxin gene and one which is located upstream of the antitoxin gene. All four toxins tested are functional in E. coli; overexpression of the toxins (in the absence of antitoxin) results in a bacteriostatic effect manifested by elongation of bacterial cells and growth arrest. The toxins have various effects on cell viability, which suggests that they may recognize different intracellular targets. Preliminary data suggest that different cellular proteases are involved in degradation of antitoxins encoded by the loci analyzed.
Links	PubMed PMC1855756 Online version:10.1128/JB.01610-06
Keywords	Antitoxins/genetics; Antitoxins/metabolism; Bacterial Toxins/genetics; Base Sequence; Conjugation, Genetic; DNA Transposable Elements; Escherichia coli/genetics; Molecular Sequence Data; Paracoccus/genetics; Plasmids; Promoter Regions, Genetic; Prophages/genetics; Replicon; Vibrio cholerae/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPN15:O64356	Contributes to	GO:0043433: negative regulation of sequence-specific DNA binding transcription factor activity	ECO:0000314:		P		From Figure 2, and 5; stabilizes the tad-ata type (toxin-antitoxin)	complete CACAO 11940
9PAST:W0Q5Y1	incorrect (CACAO)	GO:0009405: obsolete pathogenesis	ECO:0000314: direct assay evidence used in manual assertion		P		Fig 3 shows that when arabidose is added the toxin gene is getting switched on, causing E. coli cell count and density to decrease. This decrease in cell count and density indicates that toxin activity is apparent.	complete CACAO 11938
9PAST:W0Q5Y1	Contributes to	GO:0043433: negative regulation of sequence-specific DNA binding transcription factor activity	ECO:0000314: direct assay evidence used in manual assertion		P		From Figure 2, and 5; stabilizes the tad-ata type (toxin-antitoxin)	complete CACAO 11939

References

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