title: Atomic structure of a nanobody-trapped domain-swapped dimer of an amyloidogenic beta2-microglobulin variant.
abstract: Atomic-level structural investigation of the key conformational intermediates of amyloidogenesis remains a challenge. Here we demonstrate the utility of nanobodies to trap and characterize intermediates of β2-microglobulin (β2m) amyloidogenesis by X-ray crystallography. For this purpose, we selected five single domain antibodies that block the fibrillogenesis of a proteolytic amyloidogenic fragment of β2m (ΔN6β2m). The crystal structure of ΔN6β2m in complex with one of these nanobodies (Nb24) identifies domain swapping as a plausible mechanism of self-association of this amyloidogenic protein. In the swapped dimer, two extended hinge loops--corresponding to the heptapetide NHVTLSQ that forms amyloid in isolation--are unmasked and fold into a new two-stranded antiparallel β-sheet. The β-strands of this sheet are prone to self-associate and stack perpendicular to the direction of the strands to build large intermolecular β-sheets that run parallel to the axis of growing oligomers, providing an elongation mechanism by self-templated growth.
authors.affiliation: Department of Molecular and Cellular Interactions, Vlaams Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Domanska
authors.forename: Saskia
authors.initials: S
authors.lastname: Vanderhaegen
authors.forename: Vasundara
authors.initials: V
authors.lastname: Srinivasan
authors.forename: Els
authors.initials: E
authors.lastname: Pardon
authors.forename: Florine
authors.initials: F
authors.lastname: Dupeux
authors.forename: Jose A
authors.initials: JA
authors.lastname: Marquez
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.forename: Monica
authors.initials: M
authors.lastname: Stoppini
authors.forename: Lode
authors.initials: L
authors.lastname: Wyns
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
authors.forename: Jan
authors.initials: J
authors.lastname: Steyaert
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry* / Q000276:immunology / Q000648:ultrastructure; D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000915:Antibody Affinity / Q000276:immunology; D002161:Camelids, New World / Q000276:immunology; D002162:Camelus / Q000276:immunology; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D009154:Mutation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000235:genetics / Q000276:immunology
chemical_list: D000682:Amyloid; D000906:Antibodies; D001613:beta 2-Microglobulin