The MurC ligase essential for peptidoglycan biosynthesis is regulated by the serine/threonine protein kinase PknA in Corynebacterium glutamicum.
The Mur ligases play an essential role in the biosynthesis of bacterial cell-wall peptidoglycan and thus represent attractive targets for the design of novel antibacterials. These enzymes catalyze the stepwise formation of the peptide moiety of the peptidoglycan disaccharide peptide monomer unit. MurC is responsible of the addition of the first residue (L-alanine) onto the nucleotide precursor UDP-MurNAc. Phosphorylation of proteins by Ser/Thr protein kinases has recently emerged as a major physiological mechanism of regulation in prokaryotes. Herein, the hypothesis of a phosphorylation-dependent mechanism of regulation of the MurC activity was investigated in Corynebacterium glutamicum. We showed that MurC was phosphorylated in vitro by the PknA protein kinase. An analysis of the phosphoamino acid content indicated that phosphorylation exclusively occurred on threonine residues. Six phosphoacceptor residues were identified by mass spectrometry analysis, and we confirmed that mutagenesis to alanine residues totally abolished PknA-dependent phosphorylation of MurC. In vitro and in vivo ligase activity assays showed that the catalytic activity of MurC was impaired following mutation of these threonine residues. Further in vitro assays revealed that the activity of the MurC-phosphorylated isoform was severely decreased compared with the non-phosphorylated protein. To our knowledge, this is the first demonstration of a MurC ligase phosphorylation in vitro. The finding that phosphorylation is correlated with a decrease in MurC enzymatic activity could have significant consequences in the regulation of peptidoglycan biosynthesis.
Fiuza
Maria
M
Departamento de Biología Molecular, Area de Microbiología, Facultad de Biología, Universidad de León, León 24071, Spain.
Canova
Marc J
MJ
Patin
Delphine
D
Letek
Michal
M
Zanella-Cléon
Isabelle
I
Becchi
Michel
M
Mateos
Luís M
LM
Mengin-Lecreulx
Dominique
D
Molle
Virginie
V
Gil
José A
JA
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D008025:Ligases / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000096:biosynthesis* / Q000502:physiology; D010457:Peptidoglycan / Q000737:chemistry*; D019606:Phosphoamino Acids / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D017931:DNA Primers; D010457:Peptidoglycan; D019606:Phosphoamino Acids; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; D008025:Ligases; D010453:Peptide Synthases; D000409:Alanine