title: Destabilization of the dimer interface is a common consequence of diverse ALS-associated mutations in metal free SOD1.
abstract: Neurotoxic misfolding of Cu, Zn-superoxide dismutase (SOD1) is implicated in causing amyotrophic lateral sclerosis, a devastating and incurable neurodegenerative disease. Disease-linked mutations in SOD1 have been proposed to promote misfolding and aggregation by decreasing protein stability and increasing the proportion of less folded forms of the protein. Here we report direct measurement of the thermodynamic effects of chemically and structurally diverse mutations on the stability of the dimer interface for metal free (apo) SOD1 using isothermal titration calorimetry and size exclusion chromatography. Remarkably, all mutations studied, even ones distant from the dimer interface, decrease interface stability, and increase the population of monomeric SOD1. We interpret the thermodynamic data to mean that substantial structural perturbations accompany dimer dissociation, resulting in the formation of poorly packed and malleable dissociated monomers. These findings provide key information for understanding the mechanisms and energetics underlying normal maturation of SOD1, as well as toxic SOD1 misfolding pathways associated with disease. Furthermore, accurate prediction of protein-protein association remains very difficult, especially when large structural changes are involved in the process, and our findings provide a quantitative set of data for such cases, to improve modelling of protein association.
authors.affiliation: Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Broom
authors.affiliation: Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Jessica A O
authors.initials: JA
authors.lastname: Rumfeldt
authors.affiliation: Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Kenrick A
authors.initials: KA
authors.lastname: Vassall
authors.affiliation: Department of Chemistry, Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Meiering
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics; D002151:Calorimetry; D002850:Chromatography, Gel; D004795:Enzyme Stability; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics*; D000072105:Superoxide Dismutase-1; D013816:Thermodynamics
chemical_list: C000606290:SOD1 protein, human; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: apo superoxide dismutase; dissociation thermodynamics; homodimer stability; isothermal titration calorimetry; protein-protein interactions