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- Title
Substrate binding and catalytic mechanism of the Se-glycosyltransferase SenB in the biosynthesis of selenoneine.
- Authors
Huang, Wei; Song, Jun; Sun, Tianxue; He, Yue; Li, Xiang; Deng, Zixin; Long, Feng
- Abstract
Selenium is an essential multifunctional trace element in diverse organisms. The only Se-glycosyltransferase identified that catalyzes the incorporation of selenium in selenoneine biosynthesis is SenB from Variovorax paradoxus. Although the biochemical function of SenB has been investigated, its substrate specificity, structure, and catalytic mechanism have not been elucidated. Here, we reveal that SenB exhibits sugar donor promiscuity and can utilize six UDP-sugars to generate selenosugars. We report crystal structures of SenB complexed with different UDP-sugars. The key elements N20/T23/E231 contribute to the sugar donor selectivity of SenB. A proposed catalytic mechanism is tested by structure-guided mutagenesis, revealing that SenB yields selenosugars by forming C-Se glycosidic bonds via spontaneous deprotonation and disrupting Se-P bonds by nucleophilic water attack, which is initiated by the critical residue K158. Furthermore, we functionally and structurally characterize two other Se-glycosyltransferases, CbSenB from Comamonadaceae bacterium and RsSenB from Ramlibacter sp., which also exhibit sugar donor promiscuity. SenB is a Se-glycosyltransferase in the microbial biosynthesis pathway of selenoneine. Here, the authors perform the structure-function investigation, providing mechanistic insights into a two-step catalytic reaction of SenB.
- Subjects
BIOSYNTHESIS; PROTON transfer reactions; MUTAGENICITY testing; SELENOPROTEINS; TRACE elements; CRYSTAL structure
- Publication
Nature Communications, 2024, Vol 15, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-024-46065-6