title: Structural dissection of a complex Bacteroides ovatus gene locus conferring xyloglucan metabolism in the human gut.
abstract: The human gastrointestinal tract harbours myriad bacterial species, collectively termed the microbiota, that strongly influence human health. Symbiotic members of our microbiota play a pivotal role in the digestion of complex carbohydrates that are otherwise recalcitrant to assimilation. Indeed, the intrinsic human polysaccharide-degrading enzyme repertoire is limited to various starch-based substrates; more complex polysaccharides demand microbial degradation. Select Bacteroidetes are responsible for the degradation of the ubiquitous vegetable xyloglucans (XyGs), through the concerted action of cohorts of enzymes and glycan-binding proteins encoded by specific xyloglucan utilization loci (XyGULs). Extending recent (meta)genomic, transcriptomic and biochemical analyses, significant questions remain regarding the structural biology of the molecular machinery required for XyG saccharification. Here, we reveal the three-dimensional structures of an α-xylosidase, a β-glucosidase, and two α-l-arabinofuranosidases from the Bacteroides ovatus XyGUL. Aided by bespoke ligand synthesis, our analyses highlight key adaptations in these enzymes that confer individual specificity for xyloglucan side chains and dictate concerted, stepwise disassembly of xyloglucan oligosaccharides. In harness with our recent structural characterization of the vanguard endo-xyloglucanse and cell-surface glycan-binding proteins, the present analysis provides a near-complete structural view of xyloglucan recognition and catalysis by XyGUL proteins.
authors.affiliation: Department of Chemistry, York Structural Biology Laboratory, The University of York, Heslington, York YO10 5DD, UK.
authors.forename: Glyn R
authors.identifier: 0000-0002-8226-1380
authors.initials: GR
authors.lastname: Hemsworth
authors.affiliation: Department of Chemistry, York Structural Biology Laboratory, The University of York, Heslington, York YO10 5DD, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thompson
authors.affiliation: Department of Chemistry, York Structural Biology Laboratory, The University of York, Heslington, York YO10 5DD, UK.
authors.forename: Judith
authors.initials: J
authors.lastname: Stepper
authors.affiliation: Department of Chemistry, York Structural Biology Laboratory, The University of York, Heslington, York YO10 5DD, UK.
authors.forename: Łukasz F
authors.initials: ŁF
authors.lastname: Sobala
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Travis
authors.initials: T
authors.lastname: Coyle
authors.affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91 Stockholm, Sweden Michael Smith Laboratories and Department of Chemistry, University of British Columbia, 2185 East Mall, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Johan
authors.initials: J
authors.lastname: Larsbrink
authors.affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91 Stockholm, Sweden Wallenberg Wood Science Center, Royal Institute of Technology (KTH), Teknikringen 56-58, 100 44 Stockholm, Sweden.
authors.forename: Oliver
authors.initials: O
authors.lastname: Spadiut
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville Victoria 3052, Australia.
authors.forename: Ethan D
authors.initials: ED
authors.lastname: Goddard-Borger
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Stubbs
authors.affiliation: Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, 106 91 Stockholm, Sweden Michael Smith Laboratories and Department of Chemistry, University of British Columbia, 2185 East Mall, Vancouver, British Columbia, Canada V6T 1Z4 brumer@msl.ubc.ca.
authors.forename: Harry
authors.initials: H
authors.lastname: Brumer
authors.affiliation: Department of Chemistry, York Structural Biology Laboratory, The University of York, Heslington, York YO10 5DD, UK gideon.davies@york.ac.uk.
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies
mesh_terms: D001089:Arabinose / Q000031:analogs & derivatives / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001439:Bacteroides / Q000737:chemistry / Q000201:enzymology*; D018360:Crystallography, X-Ray; D041981:Gastrointestinal Tract / Q000382:microbiology; D005936:Glucans / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D013379:Substrate Specificity; D014990:Xylans / Q000378:metabolism*; D014995:Xylosidases / Q000737:chemistry; D001617:beta-Glucosidase / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D014990:Xylans; C431714:arabinofuranose; C029353:xyloglucan; D001089:Arabinose; D014995:Xylosidases; D001617:beta-Glucosidase
keywords: glycoside hydrolases; polysaccharide utilization loci; xyloglucan