Fig 4.

SodA1 is a cambialistic iron- or manganese-dependent enzyme, and SodA2 is an iron-dependent enzyme. (A) SDS-PAGE of purified recombinant SodA1 and SodA2 preparations (2 μg) previously used for crystal structure determinations (9), visualized with Coomassie brilliant blue G-250. The migration pattern of protein standards is shown. (B) In-gel SOD activity assays of recombinant SodA1 (left) and SodA2 (right) proteins (2 μg) after metal reconstitution demonstrated that both Mn²⁺-SodA1 and Fe²⁺-SodA1 are enzymatically active. Despite multiple attempts to reconstitute SodA2 with Mn²⁺, we were unable to obtain any yield of Mn²⁺-SodA2, with this lane representing resolution of a sample of apo-SodA2 in excess Mn²⁺.