Effect of oxidized βB3-crystallin peptide on lens βL- crystallin: Interaction with βB2-crystallin

PURPOSE. To investigate the interaction of oxidized βB3-crystallin peptide (residues 152-166) with β_L-crystallin and to identify peptide-interaction sites. METHODS. Peptides were oxidized by using CuSO ₄ and H₂O₂. Aggregation and light-scattering assays of bovine β_L-crystallin were conducted at 55°C and 37°C, respectively. Assays were performed in the presence of oxidized and nonoxidized βB3-crystallin peptides and in the presence of α-crystallin. Peptide-induced change in hydrophobicity was determined by bis-ANS (4,4′-dianilino-1,1′ binaphthyl-5,5′ disulfonic acid) binding study. Oxidized βB3-peptide binding sites were identified by sulfo-SBED (sulfosuccinimidyl-2-[6-(biotinamido)-2-{p-azidobenzamido}- hexanoamido] ethyl-1-3 dithiopropionate) labeling and mass spectrometric analysis. RESULTS. Aggregation and relative light-scattering of β_L-crystallin was higher in the presence of oxidized βB3-crystallin peptide than with β_L-crystallin, without oxidized peptide and with nonoxidized peptide. Enhanced aggregation was observed despite the presence of α-crystallin in the assay. Furthermore, a significant increase in aggregation and light-scattering was observed in the presence of oxidized βB3-peptide at 37°C. Bis-ANS binding to β_L-crystallin treated with oxidized βB3-peptide was two to three times higher than in the controls at 37°C. The oxidized βB3-peptide preferentially interacted with βB2-crystallin. The data were confirmed by mass spectrometric analysis. CONCLUSIONS. Oxidized βB3-peptide interacts with βB2-crystallin and enhances its aggregation and precipitation. Peptide-induced aggregation and increased hydrophobicity of the lens crystallin at 37°C are relevant to crystallin aggregation in the aging lenses.