title: Sizing up large protein complexes by electrospray ionisation-based electrophoretic mobility and native mass spectrometry: morphology selective binding of Fabs to hepatitis B virus capsids.
abstract: The capsid of hepatitis B virus (HBV) is a major viral antigen and important diagnostic indicator. HBV capsids have prominent protrusions ('spikes') on their surface and are unique in having either T = 3 or T = 4 icosahedral symmetry. Mouse monoclonal and also human polyclonal antibodies bind either near the spike apices (historically the 'α-determinant') or in the 'floor' regions between them (the 'β-determinant'). Native mass spectrometry (MS) and gas-phase electrophoretic mobility molecular analysis (GEMMA) were used to monitor the titration of HBV capsids with the antigen-binding domain (Fab) of mAb 3120, which has long defined the β-determinant. Both methods readily distinguished Fab binding to the two capsid morphologies and could provide accurate masses and dimensions for these large immune complexes, which range up to ~8 MDa. As such, native MS and GEMMA provide valuable alternatives to a more time-consuming cryo-electron microscopy analysis for preliminary characterisation of virus-antibody complexes.
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
authors.forename: Jessica Z
authors.initials: JZ
authors.lastname: Bereszczak
authors.forename: Marlene
authors.initials: M
authors.lastname: Havlik
authors.forename: Victor U
authors.initials: VU
authors.lastname: Weiss
authors.forename: Martina
authors.initials: M
authors.lastname: Marchetti-Deschmann
authors.forename: Esther
authors.initials: E
authors.lastname: van Duijn
authors.forename: Norman R
authors.initials: NR
authors.lastname: Watts
authors.forename: Paul T
authors.initials: PT
authors.lastname: Wingfield
authors.forename: Guenter
authors.initials: G
authors.lastname: Allmaier
authors.forename: Alasdair C
authors.initials: AC
authors.lastname: Steven
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
mesh_terms: D000936:Antigen-Antibody Complex / Q000737:chemistry*; D000956:Antigens, Viral / Q000737:chemistry* / Q000276:immunology; D001665:Binding Sites; D002213:Capsid / Q000737:chemistry* / Q000276:immunology; D006515:Hepatitis B virus / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D000936:Antigen-Antibody Complex; D000956:Antigens, Viral; D007140:Immunoglobulin Fab Fragments