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THE MOLECULAR CHAPERONE FUNCTION OF α‐CRYSTALLIN IS IMPAIRED BY UV PHOTOLYSIS
Author(s) -
Borkman Raymond F.,
McLaughlin Jennifer
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb02407.x
Subject(s) - chaperone (clinical) , photodissociation , chemistry , crystallin , biophysics , photochemistry , microbiology and biotechnology , biology , biochemistry , medicine , pathology
Buffer solutions of the lens protein γ‐crystallin and the enzymes aldolase and liver alcohol dehydrogenase became turbid and formed solid precipitate upon exposure to an elevated temperature of 63°C or to UV radiation at 308 nm. When α‐crystallin was added to the protein solutions in stoichiometric amounts, heat or UV irradiation did not cause turbidity, or turbidity developed much less rapidly than in the absence of α‐crystallin. Hence, normal α‐crystallin functioned as a molecular chaperone, providing protection against both UV and heat‐induced protein aggregation. When α‐crystallin was preirradiated with UV at 308 nm, its ability to function as a chaperone vis‐a‐vis both UV and heat‐induced aggregation was significantly impaired, but only at relatively high UV doses. A major effect of preirradiation of α‐crystallin was to cause interpeptide crosslinking among the αA 2 and αB 2 subunits of the α‐crystallin macromolecule. In our experiments α‐crystallin was exposed to UV doses, which resulted in 0, 50 and 90% crosslinking as judged by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. α‐Crystallin samples that were 50% and 90% crosslinked gave chaperone protection, which was increasingly impaired relative to unirradiated α‐crystallin. The results are consistent with the notion that UV irradiation of α‐crystallin results in loss of chaperone binding sites.