Synthetic LPETG-containing peptide incorporation in the Staphylococcus aureus cell-wall in a sortase A- and growth phase-dependent manner

PLoS One. 2014 Feb 19;9(2):e89260. doi: 10.1371/journal.pone.0089260. eCollection 2014.

Abstract

The majority of Staphylococcus aureus virulence- and colonization-associated surface proteins contain a pentapeptide recognition motif (LPXTG). This motif can be recognized and cleaved by sortase A (SrtA) which is a membrane-bound transpeptidase. After cleavage these proteins are covalently incorporated into the peptidoglycan. Therefore, SrtA plays a key role in S. aureus virulence. We aimed to generate a substrate mimicking this SrtA recognition motif for several purposes: to incorporate this substrate into the S. aureus cell-wall in a SrtA-dependent manner, to characterize this incorporation and to determine the effect of substrate incorporation on the incorporation of native SrtA-dependent cell-surface-associated proteins. We synthesized substrate containing the specific LPXTG motif, LPETG. As a negative control we used a scrambled version of this substrate, EGTLP and a S. aureus srtA knockout strain. Both substrates contained a fluorescence label for detection by FACScan and fluorescence microscope. A spreading assay and a competitive Luminex assay were used to determine the effect of substrate treatment on native LPXTG containing proteins deposition in the bacterial cell-wall. We demonstrate a SrtA-dependent covalent incorporation of the LPETG-containing substrate in wild type S. aureus strains and several other Gram-positive bacterial species. LPETG-containing substrate incorporation in S. aureus was growth phase-dependent and peaked at the stationary phase. This incorporation negatively correlated with srtA mRNA expression. Exogenous addition of the artificial substrate did not result in a decreased expression of native SrtA substrates (e.g. clumping factor A/B and protein A) nor induced a srtA knockout phenotype.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / genetics
  • Aminoacyltransferases / metabolism*
  • Bacterial Proteins / metabolism*
  • Cell Wall / chemistry*
  • Cysteine Endopeptidases / metabolism*
  • Flow Cytometry
  • Gene Knockout Techniques
  • Membrane Proteins / genetics*
  • Microscopy, Fluorescence
  • Oligopeptides / genetics*
  • Oligopeptides / metabolism
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Staphylococcus aureus / chemistry*
  • Statistics, Nonparametric

Substances

  • Bacterial Proteins
  • Membrane Proteins
  • Oligopeptides
  • Aminoacyltransferases
  • sortase A
  • Cysteine Endopeptidases

Grants and funding

This work was supported by ZonMW; grant title: Exploiting Staphylococcus aureus sortase for anti-infective purposes with the project number: 50-51700-98-055. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.