Catalytic Cycle of N -Acetylmuramic Acid-α-1-Phosphate Uridylyltransferase MurU of Pseudomonas aeruginosa

High Resolution Image Download MS PowerPoint Slide Peptidoglycan is the major component of the bacterial cell wall, and the cell wall is critical for bacterial survival. The cell wall undergoes constant remodeling, recycling, and biosynthesis. Importance of the peptidoglycan is underscored by the presence of both a recycling and a de novo biosynthetic pathway for the formation of key metabolites for the biosynthesis of the cell wall in the cytoplasm of Gram-negative bacteria. The two pathways experience nexus at the metabolite N -acetylmuramate-1α-uridine diphosphate ( 8 ). We describe that the enzyme MurU from Pseudomonas aeruginosa is the catalyst that produces metabolite 8, in a step that is the kinetic bottleneck in the flux of the recycling pathway. As such, MurU is a suitable target for agents that interfere with the recycling process. We disclose that this enzyme follows an ordered-sequential mechanism with UTP-Mg 2+ as the first-binding substrate, followed by N -acetylmuramate-1α-phosphate ( 7 ). We also report a series of seven high-resolution X-ray structures for MurU in complex with various substrates, metal ions, and products. The full catalytic cycle of MurU is elucidated with key structural information on the pre-catalytic complex, post-catalytic complex, metal-ion complexes, and dynamics necessary for catalysis, shedding light on the details of the chemical transformation, which enables the recycling process.