Reactive oxygen species (ROS) are highly reactive molecules that are a normal consequence of aerobic metabolism. Cellular ROS damage can induce apoptosis and spontaneous mutagenesis. Oxr1 (Oxidation resistance protein 1) is a 758 amino acid mitochondrial protein that is most likely involved in protection from oxidative damage. Oxr1 is highly conserved from yeast to humans and is specific to eukaryotes.Induced by heat and oxidative stress, the carboxyl-terminal half of Oxr1 is required for its function. Upregulation of superoxide dismutase and catalase was observed in developing drosophila mutants that lacked the gene encoding Oxr1, suggesting that oxidative stress may trigger compensatory protein expression. There are four isoforms of Oxr1 that are produced as a result of alternative splicing events.