Identification and characterization of a determinant (eep) on the Enterococcus faecalis chromosome that is involved in production of the peptide sex pheromone cAD1

Plasmid-free strains of Enterococcus faecalis secrete a peptide sex pheromo ne, cAD1, which specifically induces a mating response by donors carrying t he hemolysin plasmid pAD1 or related elements. A determinant on the E. faec alis OG1X chromosome has been found to encode a 46.5-kDa protein that plays an important role in the production of the extracellular cAD1. Wild-type E . faecalis OG1X cells harboring a plasmid chimera carrying the determinant exhibited an eightfold enhanced production of cAD1, and plasmid-free cells carrying a mutated chromosomal determinant secreted undetectable or very lo w amounts of the pheromone. The production of other pheromones such as cPD1 , cOB1, and cCF10 was also influenced, although there was no effect on the pheromone cAM373. The determinant, designated eep (for enhanced expression of pheromone), did not include the sequence of the pheromone; Its deduced p roduct (Eep) contains apparent membrane-spanning sequences; conceivably it is involved in processing a pheromone precursor structure or in some way re gulates expression or secretion.