Purification steps of MnSOD. Lane 1, low-molecular-weight markers (kDa). Lane 2, crude extract of uninduced E. coli Top10 cells harboring pHE25 plasmid. Lane 3, crude extract of E. coli Top10 harboring pHE25 plasmid induced with 0.2% arabinose for 4 h in LB medium containing 1 mM MnCl2. Lane 4, cytoplasmic extract from cells after osmotic shock. Lane 5, periplasmic protein extract resulting from osmotic shock, showing that approximately 90% of MnSOD was recovered during this step. Lane 6, fraction eluted from Q-Sepharose containing partially purified MnSOD. Lane 7, purified MnSOD from the final purification step (Superdex G-200 HR column).