Manganese catalase, ferritin-like diiron-binding domainManganese (Mn) catalase is a member of a broad superfamily of ferritin-like diiron enzymes. While many diiron enzymes catalyze dioxygen-dependent reactions, manganese catalase performs peroxide-dependent oxidation-reduction. Catalases are important antioxidant metalloenzymes that catalyze disproportionation of hydrogen peroxide, forming dioxygen and water. Manganese catalase, a nonheme type II catalase, contains a binuclear manganese cluster that catalyzes the redox dismutation of hydrogen peroxide, interconverting between dimanganese(II) [(2,2)] and dimanganese(III) [(3,3)] oxidation states during turnover. Mn catalases are found in a broad range of microorganisms in microaerophilic environments, including the mesophilic lactic acid bacteria (e.g., Lactobacillus plantarum) and bacterial and archaeal thermophiles (e.g., Thermus thermophilus and Pyrobaculum caldifontis). L. plantarum and T. thermophilus holoenzymes are homohexameric structures; each subunit contains a dimanganese active site. The manganese ions are linked by a mu 1,3-bridging glutamate carboxylate and two mu-bridging solvent oxygens that electronically couple the metal centers. Several members of this CD lack the C-terminal strands that pack against the neighboring catalytic domains as seen in L. plantarum. One such sequence, Bacillus subtilis CotJC, is known to be a component of the inner spore coat that interacts with spore coat protein, CotJA. It has been suggested that CotJC could modulate the degree of Mn SodA-dependent cross-linking of an outer coat component, or the two enzymes could serve to protect specific cellular structures during the developmental process.