Computer graphics representation of manganese superoxide dismutase, an enzyme involved in aerobic respiration. This enzyme, from the bacterium, Bacillus stearothermophilus, scavenges & decomposes the potentially toxic first reduction product, superoxide, of aerobic respiration. A family of such enzymes exists, each capable of binding to different metal ions, found at different locations in the organism. Here, a dimer of two superoxide dismutase subunits is seen bound to a single manganese atom (in green). The alpha carbon backbone of each monomer appears as either a red or blue ribbon.