Journal Article

Crystal Structures of a Multifunctional Triterpene/Flavonoid Glycosyltransferase from Medicago truncatula

Shao, Hui, Blount, Jack W, Achnine, Lahoucine, Wang, Xiaoqiang, Dixon, Richard A, He, Xianzhi

2005

Overview

Glycosylation is a ubiquitous reaction controlling the bioactivity and storage of plant natural products. Glycosylation of small molecules is catalyzed by a superfamily of glycosyltransferases (GTs) in most plant species studied to date. We present crystal structures of the UDP flavonoid/triterpene GT UGT71G1 from Medicago truncatula bound to UDP or UDP-glucose. The structures reveal the key residues involved in the recognition of donor substrate and, by comparison with other GT structures, suggest His-22 as the catalytic base and Asp-121 as a key residue that may assist deprotonation of the acceptor by forming an electron transfer chain with the catalytic base. Mutagenesis confirmed the roles of these key residues in donor substrate binding and enzyme activity. Our results provide an initial structural basis for understanding the complex substrate specificity and regiospecificity underlying the glycosylation of plant natural products and other small molecules. This information will direct future attempts to engineer bioactive compounds in crop plants to improve plant, animal, and human health and to facilitate the rational design of GTs to improve the storage and stability of novel engineered bioactive compounds.

• Publisher: American Society of Plant Biologists
• Subject: Alfalfa / Amino Acids / Amino Acids - chemistry / Amino Acids - physiology / Atomic interactions / Atoms / binding sites / Binding Sites - physiology / Bioactive compounds / Catalytic Domain / Catalytic Domain - physiology / chemistry / Crystal structure / Crystallography, X-Ray / Crystals / Enzymatic activity / enzyme activity / Enzymes / enzymology / Flavonoids / Flavonoids - metabolism / Glycosylation / glycosyltransferases / Glycosyltransferases - chemistry / Glycosyltransferases - isolation & purification / Glycosyltransferases - metabolism / Hydrogen bonds / isolation & purification / Ligands / Medicago truncatula / Medicago truncatula - chemistry / Medicago truncatula - enzymology / metabolism / Molecular Sequence Data / Molecules / Mutagenesis, Site-Directed / Phylogeny / physiology / Plant species / Plants / protein structure / Protein Structure, Quaternary / Protein Structure, Quaternary - physiology / Proteins / Sequence Homology, Amino Acid / substrate specificity / Sugars / Triterpenes / Triterpenes - metabolism / uridine diphosphate / Uridine Diphosphate - metabolism