The long-term objective of this project is to determine the effects of the presence of calcium ion on theconfiguration of the ocular lens protein alpha-crystallin. Ocular lens transparency depends on the specificpacking of proteins that are synthesized. It has been shown that a-crystallin, a major protein component ofthe ocular lens, plays an important role in maintaining the transparency of the lens. It prevents heat-inducedand photo-aggregation of other crystallins and enzymes by acting like a molecular chaperone. Thechaperone-like activity of a-crystallin is believed due to the protein providing properly placed hydrophobicsurfaces upon which the damaged protein interacts. It is thought that this chaperone-like behavior may beimportant in preventing cataract formation. Since it has been discovered that a-crystallin acts as amolecular chaperone under various denaturing conditions, research has focused on determining thismechanism of action that is thought to be protein conformation dependent. It is of interest to determineconditions which bring about this reduction in the chaperone ability of a-crystallin. It is hypothesized that acrystallin'sconfiguration, and thus its chaperone-like behavior, is affected when its configuration is alteredunder stress conditions such as exposure to near-UV radiation. This proposal (prepared in collaborationwith Dr. Lisa Hibbard (Spelman College) sets forth studies to investigate the effects of solvent ionic strengthon the configuration and chaperone-like activity of a-crystallin and the lens structural protein, b-crystallin.Since it has been recently proposed that calcium binding may have either a deleterious or pivotal role in thechaperone-like behavior of a-crystallin depending on the concentration of ion present, ionic strength studiesare relevant as it is known that the concentration of certain ions, in particular Na+ and Ca2+, can vary undergiven conditions in the ocular lens, particularly those in which cataracts are present. The combination ofincreased solvent ionic strength and exposure of aqueous solutions of a-crystallin to UV-A radiation will alsobe studied. It is of interest to determine whether the varying solvent conditions and exposure to UV radiationaffects the ability of a-crystallin to protect b-crystallin upon heating. The project will study the effects ofcalcium ion on native and damaged protein conformation using both FTIR (and deconvoluted peak data) andfar-UV CD spectra (done at Spelman College).
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