Kynurenine binds to the peptide binding region of the chaperone alpha B-crystallin

UV filters, such as kynurenine, are present in the human lens. They are spo ntaneously unstable at neutral pH and deaminate to form reactive alpha, bet a unsaturated ketones. This process becomes more prominent after the lens b arrier develops in middle age. Here we show that deaminated kynurenine reac ts primarily with histidine residues in alphaB-crystallin: a major lens pro tein that lacks cysteine. Five of the nine histidines in alphaB-crystallin were found to be conjugated with kynurenine. Furthermore, a major site of c ovalent modification was at histidine 83, which is found in the putative pe ptide binding region of alphaB-crystallin; a site crucial for its role as a chaperone. We propose that modification of alphaB-crystallin by UV filters may compromise the chaperone action of this protein. (C) 2001 Academic Pre ss.