title: Structures of mammalian ER α-glucosidase II capture the binding modes of broad-spectrum iminosugar antivirals.
abstract: The biosynthesis of enveloped viruses depends heavily on the host cell endoplasmic reticulum (ER) glycoprotein quality control (QC) machinery. This dependency exceeds the dependency of host glycoproteins, offering a window for the targeting of ERQC for the development of broad-spectrum antivirals. We determined small-angle X-ray scattering (SAXS) and crystal structures of the main ERQC enzyme, ER α-glucosidase II (α-GluII; from mouse), alone and in complex with key ligands of its catalytic cycle and antiviral iminosugars, including two that are in clinical trials for the treatment of dengue fever. The SAXS data capture the enzyme's quaternary structure and suggest a conformational rearrangement is needed for the simultaneous binding of a monoglucosylated glycan to both subunits. The X-ray structures with key catalytic cycle intermediates highlight that an insertion between the +1 and +2 subsites contributes to the enzyme's activity and substrate specificity, and reveal that the presence of d-mannose at the +1 subsite renders the acid catalyst less efficient during the cleavage of the monoglucosylated substrate. The complexes with iminosugar antivirals suggest that inhibitors targeting a conserved ring of aromatic residues between the α-GluII +1 and +2 subsites would have increased potency and selectivity, thus providing a template for further rational drug design.
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Alessandro T
authors.identifier: 0000-0001-5007-6896
authors.initials: AT
authors.lastname: Caputo
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Dominic S
authors.initials: DS
authors.lastname: Alonzi
authors.affiliation: Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy;
authors.forename: Lucia
authors.initials: L
authors.lastname: Marti
authors.affiliation: Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy;
authors.forename: Ida-Barbara
authors.initials: IB
authors.lastname: Reca
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: J L
authors.initials: JL
authors.lastname: Kiappes
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Weston B
authors.initials: WB
authors.lastname: Struwe
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Alice
authors.initials: A
authors.lastname: Cross
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Souradeep
authors.initials: S
authors.lastname: Basu
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
authors.forename: Edward D
authors.initials: ED
authors.lastname: Lowe
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; Ecole Nationale Supérieure de Chimie de Montpellier, 34296 Montpellier Cedex 5, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Darlot
authors.affiliation: Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy;
authors.forename: Angelo
authors.initials: A
authors.lastname: Santino
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; pietro.roversi@bioch.ox.ac.uk nicole.zitzmann@bioch.ox.ac.uk.
authors.forename: Pietro
authors.identifier: 0000-0001-9280-9437
authors.initials: P
authors.lastname: Roversi
authors.affiliation: Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; pietro.roversi@bioch.ox.ac.uk nicole.zitzmann@bioch.ox.ac.uk.
authors.forename: Nicole
authors.initials: N
authors.lastname: Zitzmann
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D002384:Catalysis; D018360:Crystallography, X-Ray; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D065089:Glycoside Hydrolase Inhibitors / Q000494:pharmacology*; D051379:Mice; D011487:Protein Conformation; D021122:Protein Subunits; D053838:Scattering, Small Angle; D013379:Substrate Specificity; D000520:alpha-Glucosidases / Q000737:chemistry*
chemical_list: D000998:Antiviral Agents; D065089:Glycoside Hydrolase Inhibitors; D021122:Protein Subunits; D000520:alpha-Glucosidases
keywords: ER α-glucosidase II; broad-spectrum antiviral; eukaryotic secretion; glycoprotein folding; iminosugar