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JOSEPH STAUFFER, CARL ROTHSCHILD, THADDEUS WANDEL, ABRAHAM SPECTOR; Transformation of Alpha-Crystallin Polypeptide Chains with Aging. Invest. Ophthalmol. Vis. Sci. 1974;13(2):135-146.
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Newly synthesized α-crystallin (NSα) appears relatively homogeneous with an apparent average molecular weight (MW) of 7.4 x 105 ± 3 per cent. It is composed primarily of polypeptide chains A2 and B2. Only trace amounts of B1 and small amounts of A1 can be detected. Both A1 and B1 are produced rapidly through post-translational events. Low molecular weight α-crystallin (LMWα) arises from NSα and is composed of 4 polypeptide chains, B1, B2, A1, and A2, with B1 representing approximately 11 per cent of the total polypeptide population and A1 approximately 24 per cent. Little change can be detected in the LMWα polypeptide composition isolated from three-month-old calf lens cortex or nucleus or from two-year-old steer lens nucleus. High molecular weight α-crystallin (HMWα) from calf lens periphery has a polypeptide-chain profile similar to that of LMWα. However, HMWα from calf lens nucleus shows changes in its polypeptide profile which become more pronounced in steer nucleus HMWα. Of particular interest is the appearance of two components with MW's of 17,000 and 13,000 and a splitting of the A1 urea polyacrylamide electrophoresis band. HMWα from steer nucleus was also found to contain a substantial amount of atypical A-chains with masked SH groups. It is suggested that age-dependent changes in the polypeptide-chain composition of α-crystallin affect both its size and physical homogeneity.
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