Structural characterization of a nonhydrolyzing UDP-GlcNAc 2-epimerase fromNeisseria meningitidisserogroup A

Abstract

Bacterial nonhydrolyzing UDP-N-acetylglucosamine 2-epimerases catalyze the reversible interconversion of UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylmannosamine (UDP-ManNAc). UDP-ManNAc is an important intermediate in the biosynthesis of certain cell-surface polysaccharides, including those in some pathogenic bacteria, such as Neisseria meningitidis and Streptococcus pneumoniae. Many of these epimerases are allosterically regulated by UDP-GlcNAc, which binds adjacent to the active site and is required to initiate UDP-ManNAc epimerization. Here, two crystal structures of UDP-N-acetylglucosamine 2-epimerase from Neisseria meningitidis serogroup A (NmSacA) are presented. One crystal structure is of the substrate-free enzyme, while the other structure contains UDP-GlcNAc substrate bound to the active site. Both structures form dimers as seen in similar epimerases, and substrate binding to the active site induces a large conformational change in which two Rossmann-like domains clamp down on the substrate. Unlike other epimerases, NmSacA does not require UDP-GlcNAc to instigate the epimerization of UDP-ManNAc, although UDP-GlcNAc was found to enhance the rate of epimerization. In spite of the conservation of residues involved in binding the allosteric UDP-GlcNAc observed in similar UDP-GlcNAc 2-epimerases, the structures presented here do not contain UDP-GlcNAc bound in the allosteric site. These structural results provide additional insight into the mechanism and regulation of this critical enzyme and improve the structural understanding of the ability of NmSacA to epimerize modified substrates.

KasQ an Epimerase Primes the Biosynthesis of Aminoglycoside Antibiotic Kasugamycin and KasF/H Acetyltransferases Inactivate Its Activity

“…The primary sequence and tertial structural analysis revealed that KasQ is a homolog to many non-hydrolyzing UDP-GlcNAc 2-epimerases in bacteria ( Figure S21 ), for example, 2-epimerase from E. coli (PDB entry 1vgv; 47% identity [ 19 ]), Neisseria meningitidis (PDB entry 6vlc; 44% identity [ 36 ]), Burkholderia vietnamiensis (PDB entry 5dld; 44% identity), and Bacillus subtilis (PDB entry 4fkz; 42% identity). Despite the fact that KasQ exists as dimers in solution as well as asymmetric units, only one UDP-Glc molecule is bound to one protomer of the dimer.…”

Characterization of BLUF-photoreceptors present in Acinetobacter nosocomialis

“…This enzyme catalyzes the reversible interconversion of UDP-N-acetylglucosamine (UDP-GlcNAc) to UDP-N-acetylmannosamine (UDP-ManNAc) [60], being [61]. In several pathogenic strains, such as B. anthracis, N. meningitides and S. aureus, CPSs are important virulence factors that protects bacteria from the immune system of a host and harsh environmental conditions [62][63][64]. In this sense, the UDP-N-acetylglucosamine 2epimerase could contribute to cell-surface polysaccharide synthesis in A. nosocomialis, protecting the cells in the absence of light.…”