The Type I toxin-antitoxin par locus from Enterococcus faecalis plasmid pAD1: RNA regulation by both cis- and trans-acting elements.

The pAD1 par determinant was the first Type I toxin-antitoxin system identified in Gram-positive bacteria and has recently been shown to be the prototype of a family of loci that is widespread in these organisms. All family members have (i) convergently transcribed toxin message and regulatory RNAs, (ii) three non-contiguous complementary regions for potential interaction, and (iii) intramolecular structures within the toxin message that modulate translation and transcript stability. Therefore, the detailed information available on the par locus provides a paradigm for studying the function and mechanism of regulation of the related loci.