A gain-of-function of an amyotrophic lateral sclerosis-associated Cu,Zn-superoxide dismutase mutant: An enhancement of free radical formation due to a decrease in Km for hydrogen peroxide
| ISSN: | 0027-8424 |
|---|---|
| Přístupová URL adresa: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::50267ec76d80ac9d6cb1f1e0f3f10251 https://pubmed.ncbi.nlm.nih.gov/8650157 |
| Rights: | OPEN |
| Přírůstkové číslo: | edsair.doi.dedup.....50267ec76d80ac9d6cb1f1e0f3f10251 |
| Autor: | Earl R. Stadtman, J H Kang, H S Yim, M B Yim, P B Chock, H S Kwak |
| Rok vydání: | 1996 |
| Předmět: |
DNA
Complementary Free Radicals Protein subunit Radical Mutant Molecular Sequence Data Mice Transgenic Spodoptera chemistry.chemical_compound Mice Animals Humans Enzyme kinetics Cloning Molecular chemistry.chemical_classification Multidisciplinary Spin trapping Base Sequence Superoxide Superoxide Dismutase Amyotrophic Lateral Sclerosis Hydrogen Peroxide Molecular biology Enzyme chemistry Biochemistry Mutation Dismutase Research Article |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America. 93(12) |
| ISSN: | 0027-8424 |
| Popis: | Cu,Zn-superoxide dismutase (SOD) is known to be a locus of mutation in familial amyotrophic lateral sclerosis (FALS). Transgenic mice that express a mutant Cu,Zn-SOD, Gly-93--> Ala (G93A), have been shown to develop amyotrophic lateral sclerosis (ALS) symptoms. We cloned the FALS mutant, G93A, and wild-type cDNA of human Cu,Zn-SOD, overexpressed them in Sf9 insect cells, purified the proteins, and studied their enzymic activities for catalyzing the dismutation of superoxide anions and the generation of free radicals with H2O2 as substrate. Our results showed that both enzymes contain one copper ion per subunit and have identical dismutation activity. However, the free radical-generating function of the G93A mutant, as measured by the spin trapping method, is enhanced relative to that of the wild-type enzyme, particularly at lower H2O2 concentrations. This is due to a small, but reproducible, decrease in the value of Km for H2O2 for the G93A mutant, while the kcat is identical for both enzymes. Thus, the ALS symptoms observed in G93A transgenic mice are not caused by the reduction of Cu,Zn-SOD activity with the mutant enzyme; rather, it is induced by a gain-of-function, an enhancement of the free radical-generating function. This is consistent with the x-ray crystallographic studies showing the active channel of the FALS mutant is slightly larger than that of the wild-type enzyme; thus, it is more accessible to H2O2. This gain-of-function, in part, may provide an explanation for the association between ALS and Cu,Zn-SOD mutants. |
| Databáze: | OpenAIRE |
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