The Functions and Roles of the Copper Chaperone of Superoxide Dismutase 1

Abstract

Superoxide dismutase 1 is a vital antioxidant that catalyzes the dismutation of radical oxygen to water and hydrogen peroxide. It is present in all known aerobic life, with a structural and functional homologue present in organisms as disparate as yeast and humans. Its high levels of expression and activity led to its early discovery and research, which has resulted in a vast body of literature available on its function. On top of its already significant antioxidant function, it is a regulator and signaling enzyme in many different cell systems, from immune response to cell division. Additionally, it is implicated to play a role in many diseases, notably amyotrophic lateral sclerosis (ALS), cancer, and Parkinson’s disease. The importance of Sod1 to overall life cannot be understated. Sod1 does not begin life with all these functions, however. It is first made in an immature state that lacks antioxidant activity and must undergo a maturation process to become functional. This process mainly consists of three posttranslational modifications (PTMs): addition of zinc, addition of copper, and formation of a disulfide bond. Sod1 is unable to gain these PTMs in vivo and needs the help of another protein, the copper chaperone for Sod1 (Ccs). This thesis will cover the maturation of Sod1 by Ccs as completely as possible. We will begin with the potential copper sources for Ccs as copper availability is heavily restricted by the cell. Then, we will look at the mechanism of Sod1 activation in yeast and the role Ccs plays in the addition of all three PTMs. This will then be compared to the mechanism of activation in human cells, as yeast Sod1 and yeast Ccs are structural and functional homologues of human Sod1 and human Ccs. With the normal mechanism of maturation established, we can then explore how this breaks down in ALS with common ALS-causing mutations of Sod1. Finally, we will look at a recently-discovered mutation of Ccs that has been linked to ALS-like disease symptoms.