title: Thermal fluctuations of immature SOD1 lead to separate folding and misfolding pathways.
abstract: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease involving cytotoxic conformations of Cu, Zn superoxide dismutase (SOD1). A major challenge in understanding ALS disease pathology has been the identification and atomic-level characterization of these conformers. Here, we use a combination of NMR methods to detect four distinct sparsely populated and transiently formed thermally accessible conformers in equilibrium with the native state of immature SOD1 (apoSOD1(2SH)). Structural models of two of these establish that they possess features present in the mature dimeric protein. In contrast, the other two are non-native oligomers in which the native dimer interface and the electrostatic loop mediate the formation of aberrant intermolecular interactions. Our results show that apoSOD1(2SH) has a rugged free energy landscape that codes for distinct kinetic pathways leading to either maturation or non-native association and provide a starting point for a detailed atomic-level understanding of the mechanisms of SOD1 oligomerization.
authors.affiliation: Department of Molecular Genetics, University of Toronto, Toronto, Canada.
authors.forename: Ashok
authors.initials: A
authors.lastname: Sekhar
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Canada.
authors.forename: Jessica A O
authors.initials: JA
authors.lastname: Rumfeldt
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Canada.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Broom
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Canada.
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Doyle
authors.affiliation: Department of Molecular Genetics, University of Toronto, Toronto, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bouvignies
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Canada.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Meiering
authors.affiliation: Department of Molecular Genetics, University of Toronto, Toronto, Canada.
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Kay
mesh_terms: D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding / Q000528:radiation effects*; D055503:Protein Multimerization; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D013696:Temperature
chemical_list: C000606290:SOD1 protein, human; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1
keywords: CEST; CPMG relaxation dispersion; E. coli; biophysics; human Cu, Zn superoxide dismutase; non-native oligomers; protein aggregation; structural biology; transient conformations