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Om Srivastava, Kiran Srivastava, Ekta Tiwary, ; Identification of Peptides of αA- and αB-Crystallins that are Present in Cataractous Human Lenses but Not in Age-Matched Normal Lenses. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2960.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose was to identify those peptides of αA- and αB-crystallins that only existed in water soluble (WS)- and water insoluble (WI)-protein fractions of cataractous human lenses but not in the age-matched normal lenses.
The polypeptides (molecular weight <5 kDa) were isolated from WS- and WI-proteins of 62-year-old cataractous (with nuclear cataracts) and age-matched normal human lenses by their solubilization in trichloroacetic acid (TCA). The TCA-precipitated crystallins were removed by centrifugation and the solubilized fractions were concentrated after extensive dialysis. The solubilized peptides from: (A) WS- and WI-proteins of normal lenses, and (B) WS- and WI-proteins of cataractous lenses were identically analyzed by nano-HPLC-tandom mass spectrometric method, and peptides were identified by Protein Pilot search engine (AB-Sciex) and spectra were compared using PeakView.
The number of TCA-soluble peptides identified in WS-normal, WI-normal, WS-cataractous and WI-cataractous protein fractions matched to 75, 17, 15 and 22 different proteins, respectively. The crystallin peptides identified were: WS-normal: αA, αB, βA3, βS, γC and γD, WI-normal: αA, αB, βB1 and βS, WS-cataractous: αA, αB, βB1 and βS, and WI-cataractous: αA, αB, βB1 and βS. The following peptides were exclusively present in the cataractous lenses: (A) WS-fraction: αA: residue nos.23-33,104-112; αB: residue nos. 28-42, 29-44, 108-118, and 147-175 and (B) WI-fractions: αA: residue nos.24-32, 38-50 and 55-67; αB: residue no. 30-46.
The comparative study identified the αA- and αB-peptides that existed only in WS- and WI-protein fractions of cataractous lenses but were absent in normal lenses. These model peptides will help future identification of in vivo-existing proteases that are involved in their cleavage from crystallins, and also their potential roles in aggregation and cross-linking process during cataract development.
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