Kynurenine binds to the peptide binding region of the chaperone alphaB-crystallin.
UV filters, such as kynurenine, are present in the human lens. They are spontaneously unstable at neutral pH and deaminate to form reactive alpha, beta unsaturated ketones. This process becomes more prominent after the lens barrier develops in middle age. Here we show that deaminated kynurenine reacts primarily with histidine residues in alphaB-crystallin: a major lens protein that lacks cysteine. Five of the nine histidines in alphaB-crystallin were found to be conjugated with kynurenine. Furthermore, a major site of covalent modification was at histidine 83, which is found in the putative peptide 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.
Aquilina
J A
JA
Australian Cataract Research Foundation, University of Wollongong, New South Wales, 2522, Australia.
Truscott
R J
RJ
D000375:Aging / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003459:Crystallins / Q000737:chemistry* / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007737:Kynurenine / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D018832:Molecular Chaperones; D010446:Peptide Fragments / Q000032:analysis; D010447:Peptide Hydrolases / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020539:Sequence Analysis, Protein
D003459:Crystallins; D018832:Molecular Chaperones; D010446:Peptide Fragments; D007737:Kynurenine; D006639:Histidine; D010447:Peptide Hydrolases