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theses

Alpha-synuclein (asyn) is a 140 amino acid intrinsically disordered protein that is known to form fibrils found in patients with Parkinson's Disease and Dementia with Lewy Bodies. Beta-synuclein (bsyn) is a homolog of asyn, but is not known to form fibrils and is an inhibitor of asyn aggregation under physiological conditions. Both proteins can be divided into three domains with distinct properties: N-terminal, NAC, and C-terminal. By combining domains of asyn and bsyn to form chimera structures and analyzing them through a combination of Thioflavin T binding assays, NMR, AFM, and computational studies of each expected fibril state, this study will show that chimeras with a bsyn NAC region require a reduction in pH to form fibrils, while asyn NAC chimeras are more similar to asyn in their aggregation behavior and possibly energetics within the fibril state. The regions flanking the NAC seemed to be able to regulate aggregation, where certain combinations were more inhibiting of aggregation (asyn N-terminal with bsyn C-terminal), while one combination may have actually accelerated aggregation (bsyn N-terminal with asyn C-terminal) relative to asyn. Computational studies made clear that the bsyn NAC proteins must have a different fibrillar structure than asyn, and a combination of NMR chemical shift data and energies determined from computation supported the idea that some allosteric effects may influence a possibly crucial region in the chimeras (residues ~55 to 60). This study provided more information as to how a protein like bsyn can possibly overcome the influence of inhibiting regions under non-physiological conditions to form fibrils and indicates that utilizing the properties of bsyn's C-terminal domain can lead to the proposal of especially effective inhibitors of asyn aggregation.

ETD_7581

M.S.

Includes bibliographical references

by Michael P. Olson

doi:10.7282/T3154KB5

ETD graduate

The author owns the copyright to this work.