title: A covalent homodimer probing early oligomers along amyloid aggregation.
abstract: Early oligomers are crucial in amyloid aggregation; however, due to their transient nature they are among the least structurally characterized species. We focused on the amyloidogenic protein beta2-microglobulin (β2m) whose early oligomers are still a matter of debate. An intermolecular interaction between D strands of facing β2m molecules was repeatedly observed, suggesting that such interface may be relevant for β2m dimerization. In this study, by mutating Ser33 to Cys, and assembling the disulphide-stabilized β2m homodimer (DimC33), such DD strand interface was locked. Although the isolated DimC33 display a stability similar to wt β2m under native conditions, it shows enhanced amyloid aggregation propensity. Three distinct crystal structures of DimC33 suggest that dimerization through the DD interface is instrumental for enhancing DimC33 aggregation propensity. Furthermore, the crystal structure of DimC33 in complex with the amyloid-specific dye Thioflavin-T pinpoints a second interface, which likely participates in the first steps of β2m aggregation. The present data provide new insight into β2m early steps of amyloid aggregation.
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Levon
authors.initials: L
authors.lastname: Halabelian
authors.affiliation: Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, 16146 Genova, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Relini
authors.affiliation: Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di Milano, via Celoria 2, 20133 Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Barbiroli
authors.affiliation: Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, 16146 Genova, Italy.
authors.forename: Amanda
authors.initials: A
authors.lastname: Penco
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy.|CIMAINA e Istituto CNR di Biofisica, Milano, Italy.
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ricagno
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D058227:Amyloidogenic Proteins / Q000737:chemistry / Q000378:metabolism; D003062:Codon; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D066329:Protein Aggregates; D066263:Protein Aggregation, Pathological / Q000378:metabolism; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D011994:Recombinant Proteins; D013816:Thermodynamics; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000682:Amyloid; D058227:Amyloidogenic Proteins; D003062:Codon; D066329:Protein Aggregates; D011994:Recombinant Proteins; D001613:beta 2-Microglobulin