Human beta-crystallins modified by backbone cleavage, deamidation and oxidation are prone to associate

Exp Eye Res. 2003 Sep;77(3):259-72. doi: 10.1016/s0014-4835(03)00159-3.


Information about beta-crystallins and their post-translational modifications has been scarce because of difficulties in isolating the individual beta-crystallins. These difficulties arise because the beta-crystallin sequences are highly homologous and because beta-crystallins undergo many age-related modifications that lead to a variety of molecular masses and a range of acidities for each crystallin. In this study, human beta-crystallins were isolated using several steps of chromatography both before and after two-dimensional gel electrophoresis. Many previously unidentified in vivo modifications, including deamidations among all beta-crystallins except betaB3, truncation of betaA3, betaB1 and betaA4, and oxidation of some methionines and tryptophans were located among the isolated beta-crystallins. Many modifications occurred before age 20 with modest increases in modification for beta-crystallins from lenses 20-87 years old. The tendency of the modified beta-crystallins to form non-covalent complexes was evident from their chromatographic behaviour. The presence in these complexes of betaB2-crystallin, the least modified and most soluble of the beta-crystallins, points to a possible role for betaB2 in solubilizing the more heavily modified beta-crystallins. The greater solubility of beta-crystallins compared with alpha- and gamma-crystallins in aging lenses may be due to beta-crystallin modifications and their non-covalent associations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Aging / metabolism
  • Child
  • Child, Preschool
  • Chromatography, High Pressure Liquid / methods
  • Crystallins / metabolism
  • Electrophoresis, Gel, Two-Dimensional / methods
  • Humans
  • Lens, Crystalline / metabolism*
  • Methionine / metabolism
  • Middle Aged
  • Oxidation-Reduction
  • Protein Biosynthesis
  • Tryptophan / metabolism
  • beta-Crystallin A Chain
  • beta-Crystallin B Chain / analogs & derivatives*
  • beta-Crystallin B Chain / metabolism


  • CRYBA4 protein, human
  • CRYBB1 protein, human
  • CRYBB3 protein, human
  • Crystallins
  • beta-Crystallin A Chain
  • beta-Crystallin B Chain
  • beta-crystallin B2
  • Tryptophan
  • Methionine