title: Probing the free energy landscapes of ALS disease mutants of SOD1 by NMR spectroscopy.
abstract: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that, in some cases, has been linked with mutations to the antioxidant metalloenzyme superoxide dismutase (SOD1). Although the mature form of this enzyme is highly stable and resistant to aggregation, the most immature form, lacking metal and a stabilizing intrasubunit disulfide bond, apoSOD12SH, is dynamic and hypothesized to be a major cause of toxicity in vivo. Previous solution NMR studies of wild-type apoSOD12SHhave shown that the ground state interconverts with a series of sparsely populated and transiently formed conformers, some of which have aberrant nonnative structures. Here, we study seven disease mutants of apoSOD12SHand characterize their free energy landscapes as a first step in understanding the initial stages of disease progression and, more generally, to evaluate the plasticity of low-lying protein conformational states. The mutations lead to little change in the structures and dynamics of the ground states of the mutant proteins. By contrast, the numbers of low-lying excited states that are accessible to each of the disease mutants can vary significantly, with additional conformers accessed in some cases. Our study suggests that the diversity of these structures can provide alternate interaction motifs for different mutants, establishing additional pathways for new and often aberrant intra- and intermolecular contacts. Further, it emphasizes the potential importance of conformationally excited states in directing both folding and misfolding processes.
authors: Department of Molecular Genetics, The University of Toronto, Toronto, ON, Canada M5S 1A8.|Department of Biochemistry, The University of Toronto, Toronto, ON, Canada M5S 1A8.|Department of Chemistry, The University of Toronto, Toronto, ON, Canada M5S 1A8.
authors: Ashok
authors: A
authors: Sekhar
authors: Department of Chemistry, University of Waterloo, Waterloo, ON, Canada N2L 3G1.
authors: Jessica A O
authors: JAO
authors: Rumfeldt
authors: Department of Chemistry, University of Waterloo, Waterloo, ON, Canada N2L 3G1.
authors: Helen R
authors: HR
authors: Broom
authors: Department of Chemistry, University of Waterloo, Waterloo, ON, Canada N2L 3G1.
authors: Colleen M
authors: CM
authors: Doyle
authors: Department of Biochemistry, The University of Toronto, Toronto, ON, Canada M5S 1A8.
authors: Ryan E
authors: RE
authors: Sobering
authors: Department of Chemistry, University of Waterloo, Waterloo, ON, Canada N2L 3G1.
authors: Elizabeth M
authors: EM
authors: Meiering
authors: Department of Molecular Genetics, The University of Toronto, Toronto, ON, Canada M5S 1A8; kay@pound.med.utoronto.ca.|Department of Biochemistry, The University of Toronto, Toronto, ON, Canada M5S 1A8.|Department of Chemistry, The University of Toronto, Toronto, ON, Canada M5S 1A8.|Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, ON, Canada M5G 1X8.
authors: Lewis E
authors: LE
authors: Kay
keywords: CEST NMR; CPMG NMR; conformationally excited states; free energy landscape; superoxide dismutase