Differential analysis of d-β-Asp-containing proteins found in normal and infrared irradiated rabbit lens

Although proteins are generally composed of l-α-amino acids, d-β-aspartic acid (Asp)-containing proteins have been reported in various elderly tissues. Our previous study detected several d-β-Asp-containing proteins in a rabbit lens derived from epithelial cell line by Western blot analysis of a 2D-gel using a polyclonal antibody that is highly specific for d-β-Asp-containing proteins. The identity of each spot was subsequently determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the Ms-Fit online database searching algorithm. In this study, we discovered novel d-β-Asp-containing proteins from rabbit lens. The results indicate that β-crystallin A3, β-crystallin A4, β-crystallin B1, β-crystallin B2, β-crystallin B3, γ-crystallin C, γ-crystallin D, and λ-crystallin in rabbit lens contain d-β-Asp residues. Furthermore, the occurrence of d-β-Asp residues increases with infrared ray (IR) irradiation. Additionally, some d-β-Asp-containing proteins only appear after IR irradiation. One such protein is the α-enolase, which shows homology to τ-crystallin.