MurG is an essential bacterial glycosyltransferase enzyme in Pseudomonas aeruginosa performing one of the key membrane steps of peptidoglycan synthesis catalyzing the transfer of N-acetyl glucosamine (GlcNAc) from its donor substrate, UDP-GlcNAc, to the acceptor substrate Lipid I. We have solved the crystal structure of the complex between Pseudomonas aeruginosa MurG and UDP-GlcNAc and compared it with the previously solved complex from E. coli. The structure reveals a large-scale conformational change in the relative orientations of the N- and C-terminal domains, which has the effect of widening the cofactor binding site and displacing the UDP-GlcNAc donor. These results suggest new opportunities to design potent inhibitors of peptidoglycan biosynthesis.