title: Chemical and structural analysis of an antibody folding intermediate trapped during glycan biosynthesis.
abstract: Human IgG Fc glycosylation modulates immunological effector functions such as antibody-dependent cellular cytotoxicity and phagocytosis. Engineering of Fc glycans therefore enables fine-tuning of the therapeutic properties of monoclonal antibodies. The N-linked glycans of Fc are typically complex-type, forming a network of noncovalent interactions along the protein surface of the Cγ2 domain. Here, we manipulate the mammalian glycan-processing pathway to trap IgG1 Fc at sequential stages of maturation, from oligomannose- to hybrid- to complex-type glycans, and show that the Fc is structurally stabilized following the transition of glycans from their hybrid- to complex-type state. X-ray crystallographic analysis of this hybrid-type intermediate reveals that N-linked glycans undergo conformational changes upon maturation, including a flip within the trimannosyl core. Our crystal structure of this intermediate reveals a molecular basis for antibody biogenesis and provides a template for the structure-guided engineering of the protein-glycan interface of therapeutic antibodies.
authors.affiliation: Division of Structural Biology, University of Oxford, Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN, United Kingdom. thomas.bowden@strubi.ox.ac.uk
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Bowden
authors.forename: Kavitha
authors.initials: K
authors.lastname: Baruah
authors.forename: Charlotte H
authors.initials: CH
authors.lastname: Coles
authors.forename: David J
authors.initials: DJ
authors.lastname: Harvey
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Yu
authors.forename: Byeong-Doo
authors.initials: BD
authors.lastname: Song
authors.forename: David I
authors.initials: DI
authors.lastname: Stuart
authors.forename: A Radu
authors.initials: AR
authors.lastname: Aricescu
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Scanlan
authors.forename: E Yvonne
authors.initials: EY
authors.lastname: Jones
authors.forename: Max
authors.initials: M
authors.lastname: Crispin
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D015394:Molecular Structure; D011134:Polysaccharides / Q000096:biosynthesis* / Q000737:chemistry; D017510:Protein Folding
chemical_list: D007141:Immunoglobulin Fc Fragments; D011134:Polysaccharides