Identification and molecular characterization of a gene homologous to epr (endopeptidase resistance gene) in Staphylococcus aureus

Certain Staphylococci possess a gene called epr or lif that renders the cel ls resistant to lysis by glycylglycine endopeptidase. The resistance is con ferred by modifying the amino acid composition of interpeptide chains in ce ll-wall peptidoglycan by increasing serine content and decreasing glycine c ontent. A gene homologous to epr/lif was cloned from S. aureus RN450 genomi c libraries and designated eprh. eprh was found to localize 27 bp downstrea m of a novel cell-wall hydrolase gene lytN, which is in the same orientatio n with eprh. By analogy with epr/lif, eprh is suggested to be involved in t he transfer of certain amino acids, possibly serine or amino acids other th an glycine, to interpeptide chains of cell-wall peptidoglycan. Unlike epr/l if, overexpression of eprh in S. aureus did not result in an increased resi stance to lysostaphin. Insertional inactivation of eprh or lytN by Campbell -type integration did not affect the susceptibility of the cells to lysosta phin; either. These results suggest that eprh and lytN are not essential ge nes for S. aureus growth. The physiological function of eprh remains unknow n. (C) 1998 Elsevier Science B.V. All rights reserved.