Translocase MraY Research Articles

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.

Efficient synthesis of a bacterial translocase MraY inhibitor

The bacterial translocase MraY has recently been demonstrated as a prime target for the development of new antibiotics. We describe a straightforward synthesis of a new inhibitor 1 of this enzyme. The two key steps involve a tandem nucleophilic epoxide ring opening of C2-symmetrical bis-epoxide and subsequent O-heterocyclisation, followed by O-glycosylation. The in vitro biological evaluation of 1 at 2 mM showed an 81% of inhibition of the MraY activity. Therefore, congeners of 1 should permit detailed SAR investigations for the discovery of novel antibacterials.

Towards New MraY Inhibitors: A Serine Template for Uracil and 5‐Amino‐5‐deoxyribosyl Scaffolding

AbstractThe bacterial translocase MraY is a good target for the development of new antitbiotics as it is ubiquitous and essential for bacterial growth. The goal of this work was the synthesis of simplified analogues of naturally occurring inhibitors of this enzyme to investigate the essential character of the uridine moiety of these inhibitors with regards to biological activity. Thus, the structure of the targeted enantiomerically pure N‐(uracilylpentyl)‐β‐D‐O‐(5‐amino‐5‐deoxyribosyl)‐L‐serine retains uracil and 5‐amino‐5‐deoxyribose parts linked by a serinyl template. The synthetic strategy towards this compound relies on sequential O‐glycosylation and N‐alkylation by reductive amination of a serine derivative. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Interaction of the transmembrane domain of lysis protein E from bacteriophage ϕX174 with bacterial translocase MraY and peptidyl-prolyl isomerase SlyD

The molecular target for the bacteriolytic E protein from bacteriophage X174, responsible for host cell lysis, is known to be the enzyme phospho-MurNAc-pentapeptide translocase (MraY), an integral membrane protein involved in bacterial cell wall peptidoglycan biosynthesis, with an essential role being played by peptidyl-prolyl isomerase SlyD. A synthetic 37 aa peptide E(pep), containing the N-terminal transmembrane alpha-helix of E, was found to be bacteriolytic against Bacillus licheniformis, and inhibited membrane-bound MraY. The solution conformation of E(pep) was found by circular dichroism (CD) spectroscopy to be 100 % alpha-helical. No change in the CD spectrum was observed upon addition of purified Escherichia coli SlyD, implying that SlyD does not catalyse prolyl isomerization upon E. However, E(pep) was found to be a potent inhibitor of SlyD-catalysed peptidyl-prolyl isomerization (IC(50) 0.15 microM), implying a strong interaction between E and SlyD. E(pep) was found to inhibit E. coli MraY activity when assayed in membranes (IC(50) 0.8 microM); however, no inhibition of solubilized MraY was observed, unlike nucleoside natural product inhibitor tunicamycin. These results imply that the interaction of E with MraY is not at the MraY active site, and suggest that a protein-protein interaction is formed between E and MraY at a site within the transmembrane region.

Purification and Characterization of the Bacterial MraY Translocase Catalyzing the First Membrane Step of Peptidoglycan Biosynthesis

The MraY translocase catalyzes the first membrane step of bacterial cell wall peptidoglycan synthesis (i.e. the transfer of the phospho-N-acetylmuramoyl-pentapeptide motif onto the undecaprenyl phosphate carrier lipid), a reversible reaction yielding undecaprenylpyrophosphoryl-N-acetylmuramoyl-pentapeptide (lipid intermediate I). This essential integral membrane protein, which is considered as a very promising target for the search of new antibacterial compounds, has thus far been clearly underexploited due to its intrinsic refractory nature to overexpression and purification. We here report conditions for the high level overproduction and for the first time the purification to homogeneity of milligram quantities of MraY protein. The kinetic parameters and effects of pH, salts, cations, and detergents on enzyme activity are described, taking the Bacillus subtilis MraY translocase as a model.