title: Pathological mutations H187R and E196K facilitate subdomain separation and prion protein conversion by destabilization of the native structure.
abstract: The mechanism of prion protein (PrP) conversion, the key event in prion diseases, is still not understood. We investigated how perturbations of interactions between the subdomains β1-α1-β2 and α2-α3 affect PrP conversion. In vitro fibrillization and biophysical methods were used to relate mouse PrP conversion kinetics to thermodynamic stability. We show that pathologic mutations H187R and E196K destabilize PrP (by 3.2 and 1.1 kJ/mol, respectively, at pH 7) and accelerate fibrillization. At acidic pH, the major contribution to the destabilization of PrP comes from the protonation of histidine 187 because its replacement by tyrosine led to more stable protein (by 4.2 kJ/mol at pH 4) with slower fibrillization. Furthermore, we show that the introduction of a novel histidine residue into the subdomain interface (F198H) acts as a pH-inducible switch that promotes conversion upon histidine protonation, whereas this effect is not observed when His residue is introduced at the protein surface (Y155H). We observed a strong correlation between the stability of native structure and kinetics of fibrillization of PrP variants. Our results show that pathologic mutations promote subdomain separation and suggest that stabilization of the native structure might be a viable strategy for the development of novel therapeutics for prion diseases.
authors.affiliation: *Department of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia; and EN-FIST Centre of Excellence, Ljubljana, Slovenia.
authors.forename: San
authors.initials: S
authors.lastname: Hadži
authors.affiliation: *Department of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia; and EN-FIST Centre of Excellence, Ljubljana, Slovenia.
authors.forename: Andrej
authors.initials: A
authors.lastname: Ondračka
authors.affiliation: *Department of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia; and EN-FIST Centre of Excellence, Ljubljana, Slovenia.
authors.forename: Roman
authors.initials: R
authors.lastname: Jerala
authors.affiliation: *Department of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia; and EN-FIST Centre of Excellence, Ljubljana, Slovenia iva.hafner@ki.si.
authors.forename: Iva
authors.initials: I
authors.lastname: Hafner-Bratkovič
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D017096:Prion Diseases / Q000235:genetics / Q000473:pathology*; D000072002:Prion Proteins; D011328:Prions / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
chemical_list: D000682:Amyloid; D000072002:Prion Proteins; D011328:Prions; C512657:Prnp protein, mouse
keywords: amyloid; thermodynamic stability; transmissible spongiform encephalopathies