Identification of a Phosphotransferase System of Escherichia coli Required for Growth on N -Acetylmuramic Acid

Abstract

We report here that wild-type Escherichia coli grows on N-acetylmuramic acid (MurNAc) as the sole source of carbon and energy. Analysis of mutants defective in N-acetylglucosamine (GlcNAc) catabolism revealed that the catabolic pathway for MurNAc merges into the GlcNAc pathway on the level of GlcNAc 6-phosphate. Furthermore, analysis of mutants defective in components of the phosphotransferase system (PTS) revealed that a PTS is essential for growth on MurNAc. However, neither the glucose-, mannose/glucosamine-, nor GlcNAc-specific PTS (PtsG, ManXYZ, and NagE, respectively) was found to be necessary. Instead, we identified a gene at 55 min on the E. coli chromosome that is responsible for MurNAc uptake and growth. It encodes a single polypeptide consisting of the EIIB and C domains of a so-far-uncharacterized PTS that was named murP. MurP lacks an EIIA domain and was found to require the activity of the crr-encoded enzyme IIA-glucose (EIIA Glc ), a component of the major glucose transport system for growth on MurNAc. murP deletion mutants were unable to grow on MurNAc as the sole source of carbon; however, growth was rescued by providing murP in trans expressed from an isopropylthiogalactopyranoside-inducible plasmid. A functional His 6 fusion of MurP was constructed, isolated from membranes, and identified as a polypeptide with an apparent molecular mass of 37 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Close homologs of MurP were identified in the genome of several bacteria, and we believe that these organisms might also be able to utilize MurNAc.

How Bacteria Consume Their Own Exoskeletons (Turnover and Recycling of Cell Wall Peptidoglycan)

“…Few such enzymes have been identified in nature. Interestingly, E. coli is also equipped to capture such PG products as murein tripeptide (94), Dap (7), MurNAc (26,95), and anhMurNAc (122) from the environment.…”

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

“…In E. coli, the uptake and metabolism of MurNAc are mediated by a specific phosphotransferase MurP [156]. This transporter is required for the growth of this bacterium in the presence of MurNAc as the sole carbon source [156]. MurP has not been identified in P. aeruginosa.…”

“…However, P. aeruginosa nagE (PA3761) mutants cannot grow using GlcNAc as the sole carbon source, suggesting a significant role for NagE in GlcNAc uptake [155]. In E. coli, the uptake and metabolism of MurNAc are mediated by a specific phosphotransferase MurP [156]. This transporter is required for the growth of this bacterium in the presence of MurNAc as the sole carbon source [156].…”

Recycling of the Anhydro- N -Acetylmuramic Acid Derived from Cell Wall Murein Involves a Two-Step Conversion to N -Acetylglucosamine-Phosphate

“…However, we recently learned that the gene for an etherase in E. coli has been identified (T. Jaeger, M. Arsic, and C. Mayer, submitted for publication). The gene, yfeU, is part of an operon that includes a gene coding for a new phosphotransferase, MurP, which Mayer and coworkers showed was required for growth of E. coli on MurNAc as the sole source of carbon (4). The pathway for utilization of anhMurNAc in the cytoplasm and the pathway for metabolism of MurNAc from the medium merge at the stage of formation of MurNAc-P.…”