The 1.9 Å X-ray structure of a membrane-associated glycosyltransferase involved in peptidoglycan biosynthesis is
reported. This enzyme, MurG, contains two a0b open sheet domains separated by a deep cleft. Structural analysis
suggests that the C-terminal domain contains the UDP-GlcNAc binding site while the N-terminal domain contains the
acceptor binding site and likely membrane association site. Combined with sequence data from other MurG homologs,
this structure provides insight into the residues that are important in substrate binding and catalysis. We have also noted
that a conserved region found in many UDP-sugar transferases maps to a b0a0b0a supersecondary structural motif in
the donor binding region of MurG, an observation that may be helpful in glycosyltransferase structure prediction. The
identification of a conserved structural motif involved in donor binding in different UDP-sugar transferases also suggests
that it may be possible to identify—and perhaps alter—the residues that help determine donor specificity.
Keywords: glycosyltransferase; MurG; peptidoglycan biosynthesis; X-ray crystal structure