TY - JOUR
T1 - THE REACTION OF SINGLET OXYGEN WITH PROTEINS, WITH SPECIAL REFERENCE TO CRYSTALLINS
AU - Balasubramanian, D.
AU - Du, X.
AU - Zigler, J. S.
PY - 1990/10
Y1 - 1990/10
N2 - Abstract— –Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo‐oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some “control” proteins. We find that: (1) trp residues are oxidized to N‐formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order γ > β > α and also γ A/E > γ D > γ B crystallin.
AB - Abstract— –Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo‐oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some “control” proteins. We find that: (1) trp residues are oxidized to N‐formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order γ > β > α and also γ A/E > γ D > γ B crystallin.
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U2 - 10.1111/j.1751-1097.1990.tb08679.x
DO - 10.1111/j.1751-1097.1990.tb08679.x
M3 - Article
C2 - 2089424
AN - SCOPUS:0025506306
SN - 0031-8655
VL - 52
SP - 761
EP - 768
JO - Photochemistry and Photobiology
JF - Photochemistry and Photobiology
IS - 4
ER -