Change of water-soluble-protein, urea-soluble-protein and membrane intrinsic protein in human senile cataract.

PURPOSE: To analyze the change of water-soluble-protein (WSP), urea-soluble-protein (USP) and membrane intrinsic protein (MIP) in human senile cataract.

METHODS

The water-soluble-fractions (WSF) were prepared basically according to the method of Kibbelear, et al. But in this study, 5 mmol/L B-mercaptoethanol was added to the buffer solution. The urea-soluble-fractions (USF) were prepared basically according to the method of Kibbelear, et al. Lens fiber cell membranes were purified basically according to the method of Russell, et al. SDS-PAGE were performed according to the procedure of Laemmili, et al. using resolving gel 13% and 3% stacking gel.

RESULTS

The WSP was fractionated into HM+ alpha-, beta(1-3)- and gamma-crystallin components. In nuclear cataractous lenses HM+ alpha- and B-crystallin increase, while r-crystallin decrease. The USP from clear lenses contains mainly alpha beta chains of 22KD, whereas in cataractous lenses, especially in nuclear cataractous lenses, the relative amount of the 28- and 23KD polypeptide (the components of beta-crystallin) increased markedly. Lens fiber cell MIP, clear lens and cataract lens contained the main polypeptide of 27KD (MIP) and 23KD (MP23).

CONCLUSION

The water-insoluble protein, whether in quantity or in quality, plays an important role in cataract formation.