Conformational changes of wild-type SOD1 affect the dimerization at ambient temperature

Amyotrophic lateral sclerosis is a neurodegenerative disease caused by the degeneration of lower and upper motor neurons in the brain and spinal cord. Although ALS is rare, it is the third most common neurodegenerative disease comes after Alzheimer's and Parkinson's. Since ALS has a complex molecular background, there is no effective treatment for this disease. 90% of ALS patients are sporadic, and 10% have familial disease. Mutations in more than 25 genes account for 70% of familial ALS and also explain <10% of sporadic ALS. SOD1, the second most common ALS-causative gene, encodes the dimeric antioxidant superoxide dismutase 1 protein. More than 180 mutations in the SOD1 gene are associated today with ALS. However, their mechanisms leading to ALS are not fully known. Although most of the mutations appear to have similar pathological effects on protein structure and motor neurons, they lead to different consequences in terms of disease progression. Mutations in SOD1 cause misfolding of immature intermediate form of SOD1 and disrupt the stable dimer structure of the protein; oligomerization and accumulation of the protein occurs in the cytosolic region and at the outer mitochondrial membrane of motor neurons. It has been suggested that misfolded SOD1 may interact with a voltage-dependent anion channel (VDAC1) located at the outer membrane of the mitochondria and prevents entrance of NADH, anions and ATP required for oxidative phosphorylation. On the other hand, macrophage migration inhibitory factor (MIF) is suggested to act as a chaperone for the SOD1 protein, helping misfolded SOD1 fold correctly. This thesis includes i) overexpression and purification of wild-type SOD1, SOD1G93A, MIF and VDAC1, ii) crystallization of both wild-type and mutant forms of SOD1 and iii) diffraction data collection from wild-type SOD1. In this study, we attempted to determine the first ambient temperature X-ray structure of SOD1 and identified a wild-type apo SOD1 protein structure at 4.00 Å resolution and P 21 21 21 space group.