Crystal Structure of the Pseudomonas aeruginosa MurG: UDP-GlcNAc Substrate Complex

Abstract

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.

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

“…A crystal structure of P. aeruginosa MurG has been solved in complex with its substrate, UDPGlcNAc [63].…”

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“…Further stabilization from this helix is derived from electrostatic interactions between the negatively charged phosphate and the net helix dipole (43). Other GT-B superfamily members use a similar mode of activation (48), with some anchoring the ␣-phosphate, rather than the ␤-phosphate, of the leaving group (54,55). Second, the side chain of a lysine residue (Lys-842) is positioned directly below the ␤-phosphate (Fig.…”

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“…In the P. aeruginosa MurG co-crystal with UDP-Glc N Ac, the membrane-association region is disordered. Brown et al thus hypothesised that the interaction with the acceptor Lipid I is probably needed to stabilise MurG in this region [ 47 ]. Both the N- and C-domains of MurG present a characteristic Rossmann fold (with α/β open-sheet motif), which is a signature to nucleotide-binding domains, presenting three conserved glycine-rich stretch of amino acids (termed the G-loops), proposed to stabilise the negatively charged phosphates from the substrates, independent of any metal ions [ 45 ] ( Figure 3 ).…”

“…Both the N- and C-domains of MurG present a characteristic Rossmann fold (with α/β open-sheet motif), which is a signature to nucleotide-binding domains, presenting three conserved glycine-rich stretch of amino acids (termed the G-loops), proposed to stabilise the negatively charged phosphates from the substrates, independent of any metal ions [ 45 ] ( Figure 3 ). Sequence alignment of MurG homologues pinpointed that the invariant residues are located at or near the cleft between the two domains, thus placing the active site likely along that region [ 44 , 47 , 48 ].…”

“…Despite sharing only 45% overall sequence similarity, MurG from P. aeruginosa shares many common features with its E. coli counterpart, and their crystal structures were reported to overlap closely [ 47 ] ( Figure 3 ). The substrate-binding mode of P. aeruginosa MurG is said to resemble that of conformer A in E. coli as described by Ha et al [ 44 ].…”