Thermal fluctuations of immature SOD1 lead to separate folding and misfolding pathways

• Published in: eLife Vol. 4; p. e07296
• Main Authors: Sekhar, Ashok, Rumfeldt, Jessica A O, Broom, Helen R, Doyle, Colleen M, Bouvignies, Guillaume, Meiering, Elizabeth M, Kay, Lewis E
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 23.06.2015; eLife Sciences Publication; eLife Sciences Publications, Ltd
• Subjects: Amyotrophic lateral sclerosis; Binding sites; Biochemistry, Molecular Biology; Biophysics and Structural Biology; CEST; CPMG relaxation dispersion; Crystal structure; Cytotoxicity; Free energy; human Cu, Zn superoxide dismutase; Humans; Life Sciences; Magnetic Resonance Spectroscopy; Models, Molecular; Mutation; NMR; non-native oligomer; Nuclear magnetic resonance; Oligomerization; protein aggregation; Protein Conformation; Protein folding; Protein Folding - radiation effects; Protein Multimerization; Proteins; Software; Superoxide dismutase; Superoxide Dismutase - chemistry; Superoxide Dismutase - metabolism; Superoxide Dismutase-1; Temperature; transient conformation; human Cu, Zn superoxide dismutase; CPMG relaxation dispersion; transient conformations; protein aggregation; structural biology; CEST; biophysics; non-native oligomers; E. coli
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/elife.07296

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.