Studies on the solubilization of the water-insoluble fraction from human lens and cataract

The Major in vivo Modifications of the Human Water-insoluble Lens Crystallins are Disulfide Bonds, Deamidation, Methionine Oxidation and Backbone Cleavage

“…Evidence in this study of signi®cantly greater deamidation among the higher molecular mass proteins supports deamidation as a likely contributor to formation of large aggregates. Degraded crystallins in the water-soluble portion have been reported in several studies (Srivastava, 1988;Srivastava, Srivastava and Silney, 1993;David et al, 1996;Srivastava and Srivastava, 1996;Abbasi et al, 1998;Ma et al, 1998), and gel electrophoresis of the water-insoluble fraction has indicated that low molecular mass species are even more prevalent in the water-insoluble portion (Ortwerth and Olesen, 1992). This investigation con®rmed increased degraded crystallins as a major difference between the soluble and insoluble portions.…”

“…Studies of the water-insoluble crystallins using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS±PAGE) have demonstrated extreme heterogeneity, with evidence of major components with molecular masses of 20±30 kDa, similar to the crystallins of the water-soluble portion. The gels also show a variety of components at lower and higher molecular masses, with some components too large to enter the gel (Roy and Spector, 1978a;Ortwerth and Olesen, 1992). Treatment of the waterinsoluble crystallins with dithiothreitol (DTT) only partially reduces the high molecular mass portion, indicating that some large proteins are held together by disul®de bonds, but the major reason for the high molecular masses of these crystallins is not yet known.…”

Deamidation and Disulfide Bonding in Human Lens γ-Crystallins

“…Some researchers have suggested that the modified crystallins present in the water-insoluble portion of the lens, an extremely complicated mixture that has proved difficult to characterize (Ortwerth and Olesen, 1992 ;Lund et al, 1996 ;Srivastava, 1988), may be similar to the modifications found in cataract. The goal of our laboratory is to determine, before examining cataractous lenses, exactly what modifications are present in normal lenses, and how they change as the lens ages.…”

Lens aging: Effects of crystallins

“…The lens WIS fraction of crystallin, which contains mostly a-crystallin aggregates (with some b- and g-crystallins, [3, 26, 30] is known to have increased amounts of C-terminally truncated aA- and aB-crystallins as compared to the WS fraction [30, 31, 174]. Recent studies have shown that C-terminal truncation affects oligomerization and subunit exchange, [41] as demonstrated by recombinant human aA 151 and wild-type aA-crystallins.…”