par stability determinant

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FstAT SScons.png
Secondary structure of FstAT
Symbol fstAT
Rfam RF01797
Other data
RNA type Gene; antitoxin
Domain(s) Enterococcus faecalis
SO {{{SO}}}
Fst Type I toxin-antitoxin system
Symbol Fst_toxin
Pfam PF13955
TCDB 1.C.64
OPM superfamily 254
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.[4] Their RNA secondary structures have been predicted computationally, the complementary regions appear to be presented on exposed loops for interaction.[4]

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[edit]


  1. ^ Weaver KE, Walz KD, Heine MS (November 1998). "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): 225–32. doi:10.1006/plas.1998.1368. PMID 9806859. 
  2. ^ Weaver KE, Jensen KD, Colwell A, Sriram SI (April 1996). "Functional analysis of the Enterococcus faecalis plasmid pAD1-encoded stability determinant par". Mol. Microbiol. 20 (1): 53–63. doi:10.1111/j.1365-2958.1996.tb02488.x. PMID 8861204. 
  3. ^ Shokeen S, Greenfield TJ, Ehli EA, Rasmussen J, Perrault BE, Weaver KE (March 2009). "An intramolecular upstream helix ensures the stability of a toxin-encoding RNA in Enterococcus faecalis". J. Bacteriol. 191 (5): 1528–36. doi:10.1128/JB.01316-08. PMC 2648210Freely accessible. PMID 19103923. Retrieved 2010-09-20. 
  4. ^ a b c Greenfield TJ, Ehli E, Kirshenmann T, Franch T, Gerdes K, Weaver KE (August 2000). "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): 652–60. doi:10.1046/j.1365-2958.2000.02035.x. PMID 10931358. Retrieved 2010-09-20. 
  5. ^ Gerdes K, Gultyaev AP, Franch T, Pedersen K, Mikkelsen ND (1997). "Antisense RNA-regulated programmed cell death". Annu. Rev. Genet. 31: 1–31. doi:10.1146/annurev.genet.31.1.1. PMID 9442888. 

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