Fig. 1.

The functional features of the SOD1 homodimer (PDB entry 1SPD) are all contained by the long loops IV (green) and VII (blue) that protrude from either side of the central Ig-like scaffold. These loops not only coordinate and encapsulate the Cu and Zn ions but form also the substrate channel and part of the dimer interface. In this study we analyze a monomeric variant of SOD1 where H63, H71, H80, and D83 have been mutated to S, to mimic a protein that has lost, or fails to coordinate, the native Zn²⁺ ion.