Identification of YfiH (PgeF) as a factor contributing to the maintenance of bacterial peptidoglycan composition

5 years ago

Identification of YfiH (PgeF) as a factor contributing to the maintenance of bacterial peptidoglycan composition

Manjula Reddy, Sadiya Parveen

Peptidoglycan (PG) is an essential, envelope-fortifying macromolecule of eubacterial cell walls. It is a large polymer with multiple glycan strands interconnected by short peptide chains forming a sac-like structure around cytoplasmic membrane. In most bacteria, the composition of the peptide chain is well-conserved and distinctive; in E. coli, the peptide chain length varies from two to five amino acids with a tetrapeptide consisting of L-alanine – D-glutamic acid – meso-diaminopimelic acid – D-alanine. However, it is not known how bacteria conserve the composition and sequence of peptide chains of PG. Here, we find that a conserved open reading frame of unknown function, YfiH (renamed PgeF) contributes to the maintenance of peptide composition in E. coli. Using genetic, biochemical and mass spectrometrical analyses we demonstrate that absence of yfiH results in incorporation of non-canonical amino acids, L-serine or glycine in place of L-alanine in PG sacculi leading to β-lactam – sensitivity, lethality in mutants defective in PG remodelling or recycling pathways, altered cell morphology and reduced PG synthesis. yfiH orthologs from other Gram-positive genera were able to compensate the absence of yfiH in E. coli indicating a conserved pathway in bacterial kingdom. Our results suggest editing/quality control mechanisms exist to maintain composition and integrity of bacterial peptidoglycan. Here, we identified YfiH (renamed PgeF) as a potential proofreading factor that prevents the incorporation of peptides containing non-canonical amino acids into bacterial peptidoglycan sacculus. In E. coli, absence of yfiH led to accumulation of muropeptides containing Serine or Glycine in place of L-alanine in the peptidoglycan resulting in β-lactam – sensitivity and perturbed peptidoglycan synthesis. YfiH is widely conserved suggesting editing/quality control mechanisms exist in bacteria to preserve the structure and composition of peptidoglycan.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/mmi.13730