structural basis of its biological activities are emerging (5 crystal structures are available):

1. PDB ID_2C9Z, (interesting 2 Rossmann folding, also seen in several other protein, including UDP-glucose dehydrogenase_1DLJ, GDP-mannose dehydrogenase_1MV8, T-4 phage glycosyl transferase_????, etc) Structure And Activity Of A Flavonoid 3-0 Glucosyltransferase Reveals The Basis For Plant Natural Product Modification

2. 1E8W, (a big structure, >800 AAs) Structure Determinants Of Phosphoinositide 3-Kinase Inhibition By Wortmannin, Ly294002, Quercetin, Myricetin And Staurosporine

3. 1H1I (interesting enzyme, 4 layers) Crystal Structure Of Quercetin 2,3-Dioxygenase Anaerobically Complexed With The Substrate Quercetn

4. 1GP6 (looks like 1H1I, 2 layers of b) Anthocyanidin Synthase From Arabidopsis Thaliana Complexed With Trans-Dihydroquercetin (With 30 Min Exposure To O2)

5. 2HCK Src Family Kinase Hck-Quercetin Complex ((1997). Crystal structure of the Src family tyrosine kinase Hck.. Nature, 385, 602-609)