Structure and substrate specificity of a eukaryotic fucosidase from Fusarium graminearum.

TitleStructure and substrate specificity of a eukaryotic fucosidase from Fusarium graminearum.
Publication TypeJournal Article
Year of Publication2014
AuthorsCao, H, Walton JD, Brumm P, Phillips GN
JournalThe Journal of biological chemistry
Date Published2014 Sep 12

The secreted glycoside hydrolase family 29 (GH29) α-L-fucosidase from plant pathogenic fungus Fusarium graminearum (FgFCO1) actively releases fucose from the xyloglucan fragment. We solved crystal structures of two active-site conformations, i.e. open and closed, of apoFgFCO1 and an open complex with product fucose at atomic resolution. The closed conformation supports catalysis by orienting the conserved general acid/base Glu-288 nearest the predicted glycosidic position, whereas the open conformation possibly represents an unreactive state with Glu-288 positioned away from the catalytic center. A flexible loop near the substrate binding site containing a non-conserved GGSFT sequence is ordered in the closed but not the open form. We also identified a novel C-terminal βγ-crystallin domain in FgFCO1 devoid of calcium binding motif whose homologous sequences are present in various glycoside hydrolase families. N-Glycosylated FgFCO1 adopts a monomeric state as verified by solution small angle x-ray scattering in contrast to reported multimeric fucosidases. Steady-state kinetics shows that FgFCO1 prefers α1,2 over α1,3/4 linkages and displays minimal activity with p-nitrophenyl fucoside with an acidic pH optimum of 4.6. Despite a retaining GH29 family fold, the overall specificity of FgFCO1 most closely resembles inverting GH95 α-fucosidase, which displays the highest specificity with two natural substrates harboring the Fucα1-2Gal glycosidic linkage, a xyloglucan-derived nonasaccharide, and 2'-fucosyllactose. Furthermore, FgFCO1 hydrolyzes H-disaccharide (lacking a +2 subsite sugar) at a rate 10(3)-fold slower than 2'-fucosyllactose. We demonstrated the structurally dynamic active site of FgFCO1 with flexible general acid/base Glu, a common feature shared by several bacterial GH29 fucosidases to various extents.

Pub Med Link

Alternate JournalJ. Biol. Chem.