8ZI7

Crystal structure of SrUGT76G4 in complex with Rubusoside

Summary for 8ZI7

• Entry DOI: 10.2210/pdb8zi7/pdb
• Descriptor: UGT-glycosyltransferase 76G4, SODIUM ION, 1-O-[(8alpha,9beta,10alpha,13alpha)-13-(beta-D-glucopyranosyloxy)-18-oxokaur-16-en-18-yl]-beta-D-glucopyranose, ... (8 entities in total)
• Functional Keywords: glycosyltransferase, steviol glycosides, rubusoside, complex, transferase
• Biological source: Stevia rebaudiana
• Total number of polymer chains: 1
• Total formula weight: 53164.22

Authors

Wang, Y.,Li, T.,Yin, H. (deposition date: 2024-05-13, release date: 2025-05-21, Last modification date: 2025-12-03)

Primary citation

Wang, Y.,Li, T.,Zheng, Y.,Guo, C.,Li, K.,Jia, X.,Zhu, L.,Chen, K.,Yin, H.
Characterization of Sr UGT76G4 reveals a key residue for regioselectivity and efficient Reb M synthesis.
Proc.Natl.Acad.Sci.USA, 122:e2504698122-e2504698122, 2025

PubMed Abstract: Steviol glycosides (SGs) from are prized as noncaloric sweeteners, with rebaudioside M (Reb M)-a next-generation SG known for its sucrose-like sweetness and lack of off-tastes-standing out for its superior sensory profile. However, Reb M's limited natural abundance impedes its commercial production. Here, we report the identification of a glucosyltransferase, UGT76G4 that efficiently catalyzes the conversion of Reb D to Reb M with a strong preference for C19 glycosylation. Structural and functional analyses, including X-ray crystallography, molecular dynamics simulations, and mutagenesis, revealed key residues in UGT76G4 that dictate its regioselectivity, with residue 200 playing a pivotal role. Engineered UGT76G4 variants, including Q199I/G200Y and H155S/Q199I/G200Y, enhanced Reb E and Reb D conversion efficiency by 1.46-fold and 23-fold, respectively, compared to UGT76G1. The engineered variants offer a promising pathway for increasing Reb M production, advancing biotechnological strategies for steviol glycoside biosynthesis and optimizing plant metabolic engineering approaches. Our findings deepen the understanding of SG biosynthesis and provide a basis for sustainable production of high-value sweeteners.

PubMed: 40961143
DOI: 10.1073/pnas.2504698122

Experimental method

X-RAY DIFFRACTION (2.1 Å)