Changes in albumoid protein during cataract formation

The water-insoluble albumoid protein of the human cataractous lenses was extracted in Tris/glycine buffer (pH 8.2). Subsequent homogenization in 8 M urea containing 1% beta-mercaptoethanol gave three major fractions: urea soluble fraction (USF), urea beta-mercaptoethanol-soluble fraction (U-beta-merc-IF). and urea beta-mercaptoethanol-soluble fraction (U-beta-merc-SF). The urea beta-mercaptoethanol-soluble fraction (U-beta-merc-SF) constitutes the pigmented protein of the human cataractous lenses. The amino-acid composition indicates the presence of tryptophan, high concentration of cysteine and low concentration of lysine and methionine. The brown protein is an aggregate of protein subunits which may be a protein chromophore, that directs all possible adaptive phenomenon during vision.