The state of sulphydryl groups in proteins isolated from normal and cataractous human lenses.
Individual crystallins, urea-soluble and urea-insoluble proteins were isolated from the nucleus and cortex of types I-IV cataractous lenses and normal lenses. The levels of protein sulphydryls (P-SH), disulphides (S-S), as well as surface (F-SH) and buried (S-SH) in these proteins were determined by reaction with 5, 5'-dithiotris- (2-nitrobenzoic acid) or performic acid oxidation followed by amino acid analysis. During nuclear colour development there is a progressive decrease in the sulphydryl content of the crystallins. In the nuclei of advanced cataractous lenses, the P-SH decreases to 10% of the levels found in the normal nucleus. Similar but smaller changes take place in the cortex. No specific changes were found between the crystallins, with the exception of beta S crystallin. The cysteine remains constant in all lens types suggesting no higher oxidation products are formed. There is a significant shift in the distribution of cysteine in the nucleus of type III and IV lenses. Urea-insoluble proteins are the predominant species, accounting for about 70% of the total cysteine pool. This is consistent with the accumulation of modified insoluble polypeptides during senile nuclear cataract formation.
Hum
T P
TP
Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, Australia.
Augusteyn
R C
RC
D000368:Aged; D000369:Aged, 80 and over; D002386:Cataract / Q000378:metabolism*; D002850:Chromatography, Gel; D003459:Crystallins / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D005333:Fetus / Q000378:metabolism; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism; D010084:Oxidation-Reduction; D012016:Reference Values; D012995:Solubility; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013997:Time Factors
D003459:Crystallins; D004220:Disulfides; D013438:Sulfhydryl Compounds; D003545:Cysteine