Mutations in Copper-Zinc Superoxide Dismutase that Cause Amyotrophic Lateral Sclerosis Alter the Zinc Binding Site and the Redox Behavior of the Protein

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 93; no. 22; pp. 12240 - 12244
• Main Authors: Lyons, Thomas J., Liu, Hongbin, Goto, Joy J., Nersissian, Aram, Roe, James A., Graden, Janet A., Cafe, Carla, Ellerby, Lisa M., Bredesen, Dale E., Gralla, Edith Butler, Valentine, Joan Selverstone
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 29-10-1996; National Acad Sciences; National Academy of Sciences
• Subjects: Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - enzymology; Amyotrophic Lateral Sclerosis - etiology; Apoproteins; Binding Sites; Biochemistry; Cobalt - metabolism; Copper; Copper - metabolism; Electron Spin Resonance Spectroscopy; Genetic mutation; Humans; Hydrogen-Ion Concentration; Metals; Mutagenesis, Site-Directed; Mutant proteins; Mutation; Oxidation-Reduction; Polymerase Chain Reaction; Proteins; Saccharomyces cerevisiae; Spectral bands; Spectrophotometry, Ultraviolet; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; Superoxides; Yeasts; Zinc; Zinc - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.22.12240

A series of mutant human and yeast copper-zinc superoxide dismutases has been prepared, with mutations corresponding to those found in familial amyotrophic lateral sclerosis (ALS; also known as Lou Gehrig's disease). These proteins have been characterized with respect to their metal-binding characteristics and their redox reactivities. Replacement of Zn$^{2+}$ ion in the zinc sites of several of these proteins with either Cu$^{2+}$ or Co$^{2+}$ gave metal-substituted derivatives with spectroscopic properties different from those of the analogous derivative of the wild-type proteins, indicating that the geometries of binding of these metal ions to the zinc site were affected by the mutations. Several of the ALS-associated mutant copper-zinc superoxide dismutases were also found to be reduced by ascorbate at significantly greater rate than the wild-type proteins. We conclude that similar alterations in the properties of the zinc binding site can be caused by mutations scattered throughout the protein structure. This finding may help to explain what is perhaps the most perplexing question in copper-zinc superoxide dismutase-associated familial ALS--i.e., how such a diverse set of mutations can result in the same gain of function that causes the disease.