Chaperone-like activity of a synthetic peptide toward oxidized gamma-crystallin

alpha A-Crystallin can function like a molecular chaperone. We recently rep orted that the alpha A-crystallin sequence, KFVIFLDVKHFSPEDLTVK (peptide-l, residues 70-88) by itself possesses chaperone-like (anti-aggregating) acti vity during a thermal denaturation assay. Based on the above data we propos ed that the peptide-1 sequence was the functional site in alpha A-crystalli n. In this study we investigated the specificity of peptide-1 against gamma -crystallin aggregation in the presence of H2O2 and CuSO4. Peptide-1 was ab le to completely protect against the oxidation-induced aggregation of gamma -crystallin. Removal of N-terminal Lys or the replacement of Lys with Asp ( DFVIFLDVKHFSPEDLTVK, peptide-2) did not alter the antiaggregation property of peptide-1. However, deletion of KF residues from the N-terminus of pepti de-1 resulted in a significant loss of its anti-aggregation property. Bio-g el P-30 size-exclusion chromatography of gamma-crystallin incubated with pe ptide-2 under oxidative conditions revealed that a major portion of the pep tide elutes in the void volume region along with gamma-crystallin, suggesti ng the binding of the peptide to the protein. Peptide-1 and -2 were also ab le to prevent the UV-induced aggregation of gamma-crystallin. These data in dicate that the same amino acid sequence in alpha A-crystallin is likely to be responsible for suppressing the heat-denatured, oxidatively modified an d UV-induced aggregation of proteins.