Fall Seminar Series: Dr. Elizabeth R. Gaillard
Northern Illinois Univ., Dept. of Chemistry and Biochemistry
Cataract occurs in mammals when the natural ocular lens becomes opaque and is the leading cause of blindness worldwide. The ocular lens plays a major role in the focusing optics of the human eye. It consists of concentrically packed fiber cells that are devoid of any organelles but have extremely high protein concentrations. The most abundant membrane protein is Aquaporin-0 (AQP0) which has been shown to act as a water channel. Water homeostasis is critical for maintenance of lens transparency and it is hypothesized that AQP0 acts as a “plumbing system” for the avascular lens. A known single point mutation of AQP-0 is exchange of asparagine-150 for a histidine; this mutation is associated with congenital cataract. The functional behavior (water permeability, etc.) is found to be strongly dependent on the composition of the surrounding bilayer. We have measured hydrophobicity and O2 transport profiles for artificial and native fiber cell membranes utilizing EPR spectroscopy and detect a strong barrier to polar molecule movement across the membrane. This behavior is also probed via small angle X-ray scattering. In addition, we are investigating the action of AQP0 as a water channel utilizing both SAXS and molecular dynamics simulations; it is observed that tyrosine-149 appears to play a prominent role if movement of water out of the channel.