Figure 5

Schematic representing the antioxidant potential of EC-SOD. The EC-SOD subunit exists as an active folding variant with SOD activity (aEC-SOD; filled squares) and an inactive (iEC-SOD; gray circles). Our results show that the two different subunits can combine to form dimers with variable activities. Tetrameric EC-SOD is maintained by interactions within the N-terminal region, which are likely to be unaffected by the folding of the catalytic domain. We thus propose that dimers combine to generate five different tetramers with distinct SOD activities. The relative SOD activity of each structural level is indicated below each structure. The presence or absence of the ECM-binding regions is not indicated, as this is likely not affecting the tetramer assembly.