1. Structure of an antibiotic-synthesizing UDP-glucuronate 4-epimerase MoeE5 in complex with substrate.
- Author
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Sun, Hong, Ko, Tzu-Ping, Liu, Wenting, Liu, Weidong, Zheng, Yingying, Chen, Chun-Chi, and Guo, Rey-Ting
- Subjects
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NAD (Coenzyme) , *PROTEIN structure , *CRYSTAL structure , *GLYCOSYLTRANSFERASES - Abstract
The epimerase MoeE5 from Streptomyces viridosporus converts UDP-glucuronic acid (UDP-GlcA) to UDP-galacturonic acid (UDP-GalA) to provide the first sugar in synthesizing moenomycin, a potent inhibitor against bacterial peptidoglycan glycosyltransferases. The enzyme belongs to the UDP-hexose 4-epimerase family, and uses NAD+ as its cofactor. Here we present the complex crystal structures of MoeE5/NAD+/UDP-GlcA and MoeE5/NAD+/UDP-glucose, determined at 1.48 Å and 1.66 Å resolution. The cofactor NAD+ is bound to the N-terminal Rossmann-fold domain and the substrate is bound to the smaller C-terminal domain. In both crystals the C4 atom of the sugar moiety of the substrate is in close proximity to the C4 atom of the nicotinamide of NAD+, and the O4 atom of the sugar is also hydrogen bonded to the side chain of Tyr154, suggesting a productive binding mode. As the first complex structure of this protein family with a bound UDP-GlcA in the active site, it shows an extensive hydrogen-bond network between the enzyme and the substrate. We further built a model with the product UDP-GalA, and found that the unique Arg192 of MoeE5 might play an important role in the catalytic pathway. Consequently, MoeE5 is likely a specific epimerase for UDP-GlcA to UDP-GalA conversion, rather than a promiscuous enzyme as some other family members. Image 1 • The crystal structures of MoeE5 in complex with NAD+ and sugars were determined. • Substrate disposition in the active site suggests a productive binding mode. • Extensive hydrogen-bond network to UDP-GlcA suggests highly specificity of MoeE5. • The catalytic pathway is elucidated by constructing a product model of UDP-GalA. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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