Par stability determinant explained

FstAT
Symbol:	fstAT
Rfam:	RF01797
Rna Type:	Gene antitoxin
Tax Domain:	Enterococcus faecalis

Symbol:	Fst_toxin
Fst Type I toxin-antitoxin system
Pfam:	PF13955
Tcdb:	1.C.64
Opm Family:	225
Opm Protein:	2kv5

The par stability determinant is a 400 bp locus of the pAD1 plasmid which encodes a type I toxin-antitoxin system in Enterococcus faecalis.^{[1] [2]} It was the first such plasmid addiction module to be found in gram-positive bacteria.^[3]

The par locus contains two genes: fst which encodes a 33-amino acid toxic protein and a gene for RNAII, the small RNA anti-toxin which inhibits fst translation.^[4] The two genes are found on opposite DNA strands and share a 5' region which is where they are thought to have an antisense interaction. Their RNA secondary structures have been predicted computationally, the complementary regions appear to be presented on exposed loops for interaction.

par maintains pAD1 by means of post-segregational killing (PSK). If a daughter cell does not inherit the par locus, the unstable RNAII will quickly degrade leaving the long-lived fst toxin to damage or kill the daughter cell.^[5]

See also

• Hok/sok system

Further reading

• Gerdes K, Gultyaev AP, Franch T, Pedersen K, Mikkelsen ND . Antisense RNA-regulated programmed cell death . Annu. Rev. Genet. . 31 . 1–31 . 1997 . 9442888 . 10.1146/annurev.genet.31.1.1 .
• Poulsen LK, Larsen NW, Molin S, Andersson P . A family of genes encoding a cell-killing function may be conserved in all gram-negative bacteria . Mol. Microbiol. . 3 . 11 . 1463–1472 . November 1989 . 2693900 . 10.1111/j.1365-2958.1989.tb00131.x. 41192501 .
• Hayes F . Toxins-antitoxins: plasmid maintenance, programmed cell death, and cell cycle arrest . Science . 301 . 5639 . 1496–1499 . September 2003 . 12970556 . 10.1126/science.1088157 . 2003Sci...301.1496H . 10028255 .
• Gerdes K, Rasmussen PB, Molin S . Unique type of plasmid maintenance function: postsegregational killing of plasmid-free cells . Proc. Natl. Acad. Sci. U.S.A. . 83 . 10 . 3116–3120 . May 1986 . 3517851 . 323463 . 10.1073/pnas.83.10.3116. 1986PNAS...83.3116G . free .

Notes and References

1. Weaver KE, Walz KD, Heine MS . Isolation of a derivative of Escherichia coli-Enterococcus faecalis shuttle vector pAM401 temperature sensitive for maintenance in E. faecalis and its use in evaluating the mechanism of pAD1 par-dependent plasmid stabilization . Plasmid . 40 . 3 . 225–232 . November 1998 . 9806859 . 10.1006/plas.1998.1368 .
2. Weaver KE, Jensen KD, Colwell A, Sriram SI . Functional analysis of the Enterococcus faecalis plasmid pAD1-encoded stability determinant par . Mol. Microbiol. . 20 . 1 . 53–63 . April 1996 . 8861204 . 10.1111/j.1365-2958.1996.tb02488.x. 30452609 .
3. Shokeen S, Greenfield TJ, Ehli EA, Rasmussen J, Perrault BE, Weaver KE . An intramolecular upstream helix ensures the stability of a toxin-encoding RNA in Enterococcus faecalis . J. Bacteriol. . 191 . 5 . 1528–1536 . March 2009 . 19103923 . 2648210 . 10.1128/JB.01316-08 .
4. Greenfield TJ, Ehli E, Kirshenmann T, Franch T, Gerdes K, Weaver KE . The antisense RNA of the par locus of pAD1 regulates the expression of a 33-amino-acid toxic peptide by an unusual mechanism . Mol. Microbiol. . 37 . 3 . 652–660 . August 2000 . 10931358 . 10.1046/j.1365-2958.2000.02035.x. free .
5. Gerdes K, Gultyaev AP, Franch T, Pedersen K, Mikkelsen ND . Antisense RNA-regulated programmed cell death . Annu. Rev. Genet. . 31 . 1–31 . 1997 . 9442888 . 10.1146/annurev.genet.31.1.1 .