The nature of Staphylococcus aureus MurA and MurZ and approaches for detection of peptidoglycan biosynthesis inhibitors
Staphylococcus aureus and a number of other Gram-positive organisms harbour two genes (murA and murZ) encoding UDP-N-acetylglucosamine enolpyruvyl transferase activity for catalysing the first committed step of peptidoglycan biosynthesis. We independently inactivated murA and murZ in S. aureus and established that either can sustain viability. Purification and characterization of the MurA and MurZ enzymes indicated that they are biochemically similar in vitro, consistent with similar overall structures predicted for the isozymes by molecular modelling. Nevertheless, MurA appears to be the primary enzyme utilized in the staphylococcal cell. Accordingly, murA expression was approximately five times greater than murZ expression during exponential growth, and the peptidoglycan content of S. aureus was reduced by approximately 25% following inactivation of murA, but remained almost unchanged following inactivation of murZ. Despite low level expression during normal growth, murZ expression was strongly induced (up to sixfold) following exposure to inhibitors of peptidoglycan biosynthesis, which was not observed for murA. Strains generated in this study were validated as potential tools for identifying novel anti-staphylococcal agents targeting peptidoglycan biosynthesis using known inhibitors of the pathway.
Document Type: Research Article
Affiliations: 1: Institute of Molecular and Cellular Biology and Antimicrobial Research Centre, 2: Institut de Biochimie et Biophysique Moléculaire et Cellulaire, UMR 8619 CNRS, Université de Paris-Sud, 91405 Orsay, France. 3: Institute of Membrane and Systems Biology and Antimicrobial Research Centre, 4: School of Chemistry and Antimicrobial Research Centre, University of Leeds, Leeds, LS2 9JT, UK. 5: Infectious Diseases Area, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA.
Publication date: April 1, 2009