title: Structural studies of the beta-glycosidase from Sulfolobus solfataricus in complex with covalently and noncovalently bound inhibitors.
abstract: Transition-state mimicry is increasingly important both to understand enzyme mechanism and to direct the synthesis of putative therapeutic agents. X-ray crystallography is able to provide vital information on the interactions between an enzyme and the potential inhibitor. Here we report the structures, at approximately 2 A resolution, of a family GH1 beta-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus, in complex with both covalently (derived from 2-fluoro-glycosides) and noncovalently (hydroximolactam) bound inhibitors. The enzyme has broad specificity, accommodating both gluco- and galacto-configured substrates, and the crystallographic data demonstrate that the only difference in the way these ligands bind lies in the interactions between Gln18, Glu432, and Trp433, and the hydroxyl group at the O3 and O4 positions. Inhibition by the differently configured ligands was also shown to be extremely similar, with K(i) values of 1.04 and 1.08 microM for the gluco and galacto epimers, respectively. The noncovalently bound inhibitors have a trigonal anomeric carbon, adopt a (4)H(3) (half-chair) conformation, and an interaction is formed between O2 and the catalytic nucleophile, all of which contribute to (partial) mimicry of the oxocarbenium-ion-like transition state. The inhibition of the beta-glycosidase from S. solfataricus by hydroximolactams is discussed in light of the emerging work on family GH1 glycosidase inhibition by a spectrum of putative transition-state mimics.
authors.affiliation: Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5YW, United Kingdom.
authors.forename: Tracey M
authors.initials: TM
authors.lastname: Gloster
authors.forename: Shirley
authors.initials: S
authors.lastname: Roberts
authors.forename: Valérie M-A
authors.initials: VM
authors.lastname: Ducros
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Perugino
authors.forename: Mosè
authors.initials: M
authors.lastname: Rossi
authors.forename: Roland
authors.initials: R
authors.lastname: Hoos
authors.forename: Marco
authors.initials: M
authors.lastname: Moracci
authors.forename: Andrea
authors.initials: A
authors.lastname: Vasella
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies
mesh_terms: D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D005959:Glucosidases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D046911:Macromolecular Substances; D008958:Models, Molecular; D015394:Molecular Structure; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D013816:Thermodynamics; D047090:beta-Lactams / Q000737:chemistry
chemical_list: D004791:Enzyme Inhibitors; D006027:Glycosides; D008024:Ligands; D046911:Macromolecular Substances; D047090:beta-Lactams; D005959:Glucosidases; C104851:Sulfolobus solfataricus beta-glycosidase