Photooxidation of lens crystallins has been found to induce significant changes in their tertiary structures, and is likely to play an important role in the crosslinking and aggregation of these proteins observed in aged and cataractous human lenses. Irradiation of calf lens α-, β-and γ-crystallins in the presence of visible light and the photosensitizers methylene blue or riboflavin and by irradiation with 300 nm radiation has been investigated. Of the three classes of crystallins, only the monomeric γ-crystallins have been found to undergo partial insolubilization in photosensitized reactions. The insoluble material is highly crosslinked by nondisulfide linkages. Moreover, change in the molecular charge of the protein is observed. Analysis of the soluble fraction of the irradiated γ-crystallin, by circular dichroism and fluorescence spectroscopy, reveals changes in the tertiary structure of the protein, probably involving a partial unfolding of the molecule. Active species of molecular oxygen play a role in these structural modifications. The change in conformation is different for each photosensitizer used, suggesting that the sensitizer-protein complexation may be important.
|Number of pages||6|
|Journal||Proceedings of SPIE - The International Society for Optical Engineering|
|State||Published - Feb 19 1988|