IN-VITRO CROSS-LINKING OF CALF LENS ALPHA-CRYSTALLIN BY MALONDIALDEHYDE

The effect of malondialdehyde on structural features of bovine a-cryst allin has been investigated by absorption and fluorescence spectroscop y as well as by far-UV circular dichroism. Experimental evidence sugge sts the occurrence of intermolecular cross-linking induced by malondia ldehyde. This cross-linking does not seem to affect the tryptophan env ironment, as suggested by intrinsic protein fluorescence. On the contr ary, the time dependence of far-UV dichroic activity indicates that th e cross-linking is accompanied by a secondary structure change. The fo rmation of high molecular mass aggregates, evidenced by electrophoresi s in denaturing conditions, leads to irreversible x-crystallin aggrega tion due to extensive intermolecular cross-linking. Since malondialdeh yde is produced in vivo as a breakdown product of lipid peroxidation, the possible involvement of this molecule in the pathological mechanis m of cataract formation has been briefly discussed. (C) Munksgaard 199 4.