title: An antibody that prevents serpin polymerisation acts by inducing a novel allosteric behaviour.
abstract: Serpins are important regulators of proteolytic pathways with an antiprotease activity that involves a conformational transition from a metastable to a hyperstable state. Certain mutations permit the transition to occur in the absence of a protease; when associated with an intermolecular interaction, this yields linear polymers of hyperstable serpin molecules, which accumulate at the site of synthesis. This is the basis of many pathologies termed the serpinopathies. We have previously identified a monoclonal antibody (mAb4B12) that, in single-chain form, blocks α1-antitrypsin (α1-AT) polymerisation in cells. Here, we describe the structural basis for this activity. The mAb4B12 epitope was found to encompass residues Glu32, Glu39 and His43 on helix A and Leu306 on helix I. This is not a region typically associated with the serpin mechanism of conformational change, and correspondingly the epitope was present in all tested structural forms of the protein. Antibody binding rendered β-sheet A - on the opposite face of the molecule - more liable to adopt an 'open' state, mediated by changes distal to the breach region and proximal to helix F. The allosteric propagation of induced changes through the molecule was evidenced by an increased rate of peptide incorporation and destabilisation of a preformed serpin-enzyme complex following mAb4B12 binding. These data suggest that prematurely shifting the β-sheet A equilibrium towards the 'open' state out of sequence with other changes suppresses polymer formation. This work identifies a region potentially exploitable for a rational design of ligands that is able to dynamically influence α1-AT polymerisation.
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Neda
authors.initials: N
authors.lastname: Motamedi-Shad
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Alistair M
authors.initials: AM
authors.lastname: Jagger
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Liedtke
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K. Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, U.K.
authors.forename: Sarah V
authors.initials: SV
authors.lastname: Faull
authors.affiliation: Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Arjun Scott
authors.initials: AS
authors.lastname: Nanda
authors.affiliation: Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K. London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, U.K. School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
authors.forename: Enrico
authors.initials: E
authors.lastname: Salvadori
authors.affiliation: Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Wort
authors.affiliation: Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K. London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, U.K.
authors.forename: Christopher W M
authors.initials: CW
authors.lastname: Kay
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Narinder
authors.initials: N
authors.lastname: Heyer-Chauhan
authors.affiliation: Department of Biology and Biotechnologies 'Charles Darwin', Sapienza University of Rome, Rome 00185, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Miranda
authors.affiliation: Departamento de Biologia Celular, Genetica y Fisiologia, Facultad de Ciencias, Campus Teatinos, Universidad de Malaga, Malaga 29071, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Perez
authors.affiliation: Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/Medical Research Council Building, Hills Road, Cambridge CB2 0XY, U.K.
authors.forename: Adriana
authors.initials: A
authors.lastname: Ordóñez
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: Imran
authors.initials: I
authors.lastname: Haq
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: James A
authors.initials: JA
authors.lastname: Irving
authors.affiliation: Centre for Respiratory Biology, UCL Respiratory, University College London, London WC1E 6JF, U.K. Institute of Structural and Molecular Biology/Birkbeck, University of London, London WC1E 7HX, U.K.
authors.forename: David A
authors.initials: DA
authors.lastname: Lomas
mesh_terms: D000494:Allosteric Regulation; D000911:Antibodies, Monoclonal / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004797:Enzyme-Linked Immunosorbent Assay; D031541:Fluorescence Resonance Energy Transfer; D016297:Mutagenesis, Site-Directed; D058105:Polymerization; D015843:Serpins / Q000378:metabolism*; D013696:Temperature; D000515:alpha 1-Antitrypsin / Q000737:chemistry / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D015843:Serpins; D000515:alpha 1-Antitrypsin
keywords: allosteric regulation; antibodies; protein aggregation; protein conformation; protein–protein interactions; serpin