DIFFERENCES IN SUSCEPTIBILITY BETWEEN CRYSTALLINS AND NONLENTICULAR PROTEINS TO COPPER AND H2O2-MEDIATED PEPTIDE-BOND CLEAVAGE

The relative susceptibilities of lenticular proteins (α β and γcrystallins) and a number of proteins of non-lenticular origin, to hydroxyl radical-mediated peptide bond cleavage were compared. The non-lenticular proteins (bovine serum albumin, ovalbumin, alcohol dehydrogenase, lysozyme, thyroglobulin, βamylase, haemoglobin and carbonic anhydrase) were readily cleaved into acid-soluble fragments following 5 hours treatment with copper ions and hydrogen peroxide. In contrast the crystallins were almost totally unaffected by similar treatment. When αcrystallin was pre-treated with acid or cleaved into large fragments with cyanogen bromide it became susceptible to hydroxyl radical attack, yet heating the protein did not diminish its resistance. It is suggested that the resistance of αcrystallin to the copper/peroxide-mediated fragmentation may be dependent on the conformation of the protein. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.