title: Reduction of conformational mobility and aggregation in W60G β2-microglobulin: assessment by 15N NMR relaxation.
abstract: The amyloid pathology associated with long-term haemodialysis is due to the deposition of β2-microglobulin, the non-polymorphic light chain of class I major histocompatibility complex, that accumulates at bone joints into amyloid fibrils. Several lines of evidence show the relevance of the tryptophan residue at position 60 for the fibrillogenic transition of the protein. A comparative (15)N NMR relaxation analysis is presented for wild-type human β2-microglobulin and W60G β2-microglobulin, i.e. the mutant with a glycyne replacing the natural tryptophan residue at position 60. The experimental data, collected at 11.4 T and 310 K, were analyzed by means of the reduced spectral density approach. Molecular dynamics (MD) simulations and corresponding thermodynamic integration, together with hydrodynamic calculations were performed to support data interpretation. The analysis results for the mutant protein are consistent with a reduced aggregation with respect to the wild-type counterpart, as a consequence of an increased conformational rigidity probed by either NMR relaxation and MD simulations. Although dynamics in solution is other than fibrillar competence, the assessed properties of the mutant protein can be related with its reduced ability of forming fibrils when seeded in 20% trifluoroethanol.
authors.affiliation: Dipartimento di Scienze Mediche e Biologiche, Università di Udine, Udine, Italy; Department of Genetics and Bioengineering, Yeditepe University, Istanbul, Turkey.
authors.forename: Devrim
authors.initials: D
authors.lastname: Gümral
authors.forename: Federico
authors.initials: F
authors.lastname: Fogolari
authors.forename: Alessandra
authors.initials: A
authors.lastname: Corazza
authors.forename: Paolo
authors.initials: P
authors.lastname: Viglino
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.forename: Monica
authors.initials: M
authors.lastname: Stoppini
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
authors.forename: Gennaro
authors.initials: G
authors.lastname: Esposito
mesh_terms: D006801:Humans; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D013816:Thermodynamics; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000235:genetics
chemical_list: D009587:Nitrogen Isotopes; D001613:beta 2-Microglobulin
keywords: 15N; 1H; NMR; NMR 15N relaxation; amyloid; beta2-microglobulin; fibrillogenesis; protein dynamics; spectral density mapping