ANALYSIS OF THE STAPHYLOCOCCUS-EPIDERMIDIS GENES EPIF, EPIE, AND EPIGINVOLVED IN EPIDERMIN IMMUNITY

The lantibiotic epidermin is produced by Staphylococcus epidermidis Tu 3298. The known genes involved in epidermin biosynthesis and regulatio n are organized as operons (epiABCD and epiQP) that are encoded on the 54-kb plasmid pTu32. Here we describe the characterization of a DNA r egion that mediates immunity and increased epidermin production, locat ed upstream of the structural gene epiA. The sequence of a 2.6-kb DNA fragment revealed three open reading frames, epiF, -E, and -G, which m ay form an operon, In the cloning host Staphylococcus carnosus, the th ree genes mediated an increased tolerance to epidermin, and the highes t level of immunity (sevenfold) was achieved with S, carnosus carrying epiFEG and epiQ. The promoter of the first gene, epiF, responded to t he activator protein EpiQ and contained a palindromic sequence similar to the EpiQ binding site of the epiA promoter, which is also activate d by EpiQ. Inactivation of epiF, -E, or -G resulted in the complete lo ss of the immunity phenotype, An epidermin-sensitive S. epidermidis Tu 3298 mutant was complemented by a DNA fragment containing all three ge nes, When the epiFEG genes were cloned together with plasmid pTepi14, containing the biosynthetic genes epiABCDQP, the level of epidermin pr oduction was approximately fivefold higher. The proteins EpiF, -E, and -G are similar in deduced sequence and proposed structure to the comp onents of various ABC transporter systems, EpiF is a hydrophilic prote in with conserved ATP-binding sites, while EpiE and -G have six altern ating hydrophobic regions and very likely constitute the integral memb rane domains, When EpiF was overproduced in S. carnosus, it was at lea st partially associated with the cytoplasmic membrane. A potential mec hanism for how EpiFEG mediates immunity is discussed.