Proc Natl Acad Sci U S A 1994 Oct 11;91(21):9906-10
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
Sequences encoding three copper-zinc superoxide dismutase (CuZnSOD) mutantproteins analogous to those coded for in familial amyotrophic lateral sclerosis(fALS) were constructed in the Saccharomyces cerevisiae CuZnSOD gene andexpressed in yeast lacking CuZnSOD (sod1-). Gly85–>Arg CuZnSOD failed to rescue the oxygen-sensitive phenotype of sod1- yeast, but Gly93–>AlaCuZnSOD and Lys100–>Gly CuZnSOD were apparently fully functional in vivo.The Gly85–>Arg mutant protein was purified and its metal-binding propertiesand SOD activity were found to be significantly altered relative to wildtype. The Gly93–>Ala CuZnSOD was likewise purified but, in contrast, demonstrated metal-binding comparable to wild type and activity 80% that of wild type. These results suggest that SOD activity of human fALS mutantCuZnSODs may vary considerably in vivo, with at least some of them retaining a considerable amount of activity. Alternative theories to increased free-radicaldamage should be considered in attempting to explain fALS.