TY - JOUR
T1 - Structural characterization of a nonhydrolyzing UDP-GlcNAc 2-epimerase from Neisseria meningitidis serogroup A
AU - Hurlburt, Nicholas K.
AU - Guan, Jasper
AU - Ong, Hoonsan
AU - Yu, Hai
AU - Chen, Xi
AU - Fisher, Andrew J.
N1 - Funding Information:
This work was partially supported by funding from US National Institutes of Health (NIH) grants (R01GM094523 to XC and U01GM125288 to HY). AJF is partially supported by a United States Department of Agriculture National Institute of Food and Agriculture Hatch Grant (CA-D-MCB-2310-H). NKH was partially supported by NIH training grant T32GM007377. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research and by the NIH National Institute of General Medical Sciences (NIGMS) (P41GM103393). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIH or NIGMS.
PY - 2020/11/1
Y1 - 2020/11/1
N2 - 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.
AB - 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.
KW - epimerases
KW - epimerization
KW - Neisseria meningitidis
KW - Rossmann fold
KW - UDP-GlcNAc
KW - UDP-ManNAc
KW - X-ray crystallography
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U2 - 10.1107/S2053230X20013680
DO - 10.1107/S2053230X20013680
M3 - Article
C2 - 33135674
AN - SCOPUS:85095392766
VL - 76
SP - 557
EP - 567
JO - Acta Crystallographica Section F:Structural Biology Communications
JF - Acta Crystallographica Section F:Structural Biology Communications
SN - 1744-3091
ER -