The reaction of methylglyoxal with human and bovine lens proteins.
Methylglyoxal is an endogenous metabolite that increases in diabetes and has been implicated in some of its long-term complications such as retinopathy, neuropathy and cataract. We investigated the reaction of methylglyoxal with isolated human and bovine lens crystallins (alpha, beta H, beta L and gamma). After 7 days incubation at 37 degrees C and pH 6.9, the reaction of methylglyoxal with lens proteins yielded stable adducts that exhibited fluorescent properties. SDS-polyacrylamide gel electrophoresis was used to monitor aggregation and crosslinking of the modified protein and autoradiography showed that [14C]methylglyoxal was incorporated into all the protein bands. Bovine gamma-crystallin was the most reactive towards methylglyoxal. Reaction of methylglyoxal with bovine gamma II-crystallin, which is found mainly in the lens nucleus, could alter the change surface network of the molecule, resulting in aggregation, increased light scattering and hence cataract. Modification of gamma II-crystallin by methylglyoxal produced an overall loss of positive charge and an increase in molecular weight and non-disulfide covalent crosslinking. Amino acid analysis of the modified gamma II-crystallin showed a loss of 47% of arginine residues.
Riley
M L
ML
Nuffield Laboratory of Ophthalmology, University of Oxford, UK.
Harding
J J
JJ
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001345:Autoradiography; D001894:Borohydrides; D002417:Cattle; D003459:Crystallins / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D011765:Pyruvaldehyde / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature
D000596:Amino Acids; D001894:Borohydrides; D003459:Crystallins; D011765:Pyruvaldehyde; C025364:sodium borohydride