Abstract:
The human lens β- and γ-crystallins, are fantastically stable, soluble, and refractive. These properties allow them to form a transparent tissue specially designed to focus light. Over time, they accumulate post-translational modifications (PTMs) from damaging species, such as metal ions and ionizing radiation. These PTMs alter the biophysical properties of the lens proteins until their solubility fails and light-scattering aggregates form. These large particles form age-related cataract - the leading cause of blindness worldwide. Here, I show my inves- tigation into the boundaries of human γS-crystallin (HγS) solubility after the accumulation of PTMs. I show that exposure to high doses of γ irradiation causes extensive oxidation, but HγS largely resists unfolding. Additionally, four HγS variants that mimic progressive deamidation and are prone to oxidation show no changes in the slow dynamics. However, the increased surface charge leads to unfavorable electrostatics. The work described in this thesis will help unravel the structural determinants of cataract.