Oxidative stress and aging in Caenorhabditis elegans.

Much attention has been focused on the hypothesis that oxidative damage plays in cellular and organismal aging. A mev-1 (kn1) mutant of Caenorhabditis elegans, isolated on the basis of its methyl viologen (paraquat) hypersensitivity, is also hypersensitive to elevated oxygen levels. Unlike the wild type, its life span decreases dramatically as oxygen concentrations are increased from 1% to 60%. Strains, which bear this mutation, accumulate fluorescent materials and protein carbonyl groups, markers of aging, at faster rates than the wild type. We have cloned mev-1 gene by transformation rescue and found that it is, in fact, the previously sequenced gene (cyt-1) that encodes succinate dehydrogenase cytochrome b. A missense mutation abolishes complex II activity in the mitochondrial membrane but not succinate dehydrogenase enzyme activity per se. These data suggest that CYT-1 directly participates in electron transport from FADH2 to coenzyme Q. Moreover, mutational inactivation of this process renders animals susceptible to oxidative stress and, as a result, leads to premature aging.