5u6m
From Proteopedia
Crystal structure of UDP-glucosyltransferase, UGT74F2, with UDP and salicylic acid
Structural highlights
Function[U74F2_ARATH] Glycosyltransferase that glucosylates benzoic acid and derivatives. Substrate preference is benzoic acid > salicylic acid (SA) > 3-hydroxybenzoic acid > 4-hydroxybenzoic acid. Catalyzes the formation of both SA 2-O-beta-D-glucoside (SAG) and SA glucose ester (SGE). Has high affinity for the tryptophan precursor anthranilate. Catalyzes the formation of anthranilate glucose ester. Is the major source of this activity in the plant.[1] [2] [3] [4] [5] Publication Abstract from PubMedSalicylic acid (SA) is a signaling molecule utilized by plants in response to various stresses. Through conjugation with small organic molecules such as glucose, an inactive form of SA is generated which can be transported into and stored in plant vacuoles. In the model organism Arabidopsis thaliana, SA glucose conjugates are formed by two homologous enzymes (UGT74F1 and UGT74F2) that transfer glucose from UDP-glucose to SA. Despite being 77% identical and with conserved active site residues, these enzymes catalyze the formation of different products: UGT74F1 forms salicylic acid glucoside (SAG), while UGT74F2 forms primarily salicylic acid glucose ester (SGE). The position of the glucose on the aglycone determines how SA is stored, further metabolized, and contributes to a defense response. We determined the crystal structures of the UGT74F2 wild-type and T15S mutant enzymes, in different substrate/product complexes. On the basis of the crystal structures and the effect on enzyme activity of mutations in the SA binding site, we propose the catalytic mechanism of SGE and SAG formation and that SA binds to the active site in two conformations, with each enzyme selecting a certain binding mode of SA. Additionally, we show that two threonines are key determinants of product specificity. Differences in salicylic acid glucose conjugations by UGT74F1 and UGT74F2 from Arabidopsis thaliana.,George Thompson AM, Iancu CV, Neet KE, Dean JV, Choe JY Sci Rep. 2017 Apr 20;7:46629. doi: 10.1038/srep46629. PMID:28425481[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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