In order to characterize the proteins and polypeptides in human lenses with senile cataract, soluble proteins in the cataractous lenses were isolated and fractionated by a DEAE-cellulose column chromatography, native polyacrylamide electrophoresis (PAGE) and sodium dodecyl (SDS) PAGE, and the results were compared with those of normal human lenses.
1) As compared with those in normal human lenses, soluble protein contents were significantly decreased by 2207o and insoluble protein contents were markedly in-creased by approximately 3-fold in lenses with senile cataract.
2) Soluble proteins in both normal and the cataractous lenses were separated into 7 peaks, respectively. Protein peaks Vb and VII eluted in the cataractous lenses were not found in normal human lenses, suggesting that the two peaks may be responsible, in part, for pathogenesis of senile cataract.
3) SDS-PAGE of the. cataractous lens protein peaks revealed that protein peaks I, II and III diminished in lenses with senile cataract were composed of low molecular weight (LMW) polypeptides (15,000-28,000) and relatively large amount of high molecular weight (HMW) polypeptides (45,000 or above), and protein peaks Va and Vb increased in lenses with senile cataract were made up of LMW polypeptide (15,000-21,000) and relatively large amount of HMW polypeptides. These results indicated that the LMW and HMW polypeptides in protein peaks I, II and III appeared to be associated to form protein molecules in peak Va and Vb when normal human lenses were transformed into senile cataract. It could be suggested that these processes might play an important role in pathogenesis and maintenance of senile cataract.
4) Protein and polypeptide bands separated by native-PAGE and SDS-PAGE appeared to be distinctive in normal lenses, but not distinctive and diffuse in the cataractous lenses. These results indicated that, differing from those of normal lenses, polypeptides in the cataractous lenses were linked not only with the disulfide (SS) linkages, but also with non-SS, covalent linkages. Non-SS covalent changes in soluble protein molecules of lenses have been suggested to play a part of role in lens opacification.
|