SOD1 and amyotrophic lateral sclerosis: Further to this, altered interaction with Cu also provides a plausible mechanism by which SOD1 may contribute to motor neuron decline in sporadic cases of ALS that do not involve mutant SOD1; even in the absence of a disease-causing mutation, the bioavailability of Cu to SOD1 is an important determinant of the protein’s stability and structure36, and mis-folded and aggregated SOD1 is present in sporadic cases of ALS37.