Deamidation of Asn-143 of gammaS crystallin from protein aggregates of thehuman lens

Purpose. Determine if gammaS crystallin is preferentially deamidated in the high molecular weight aggregate fraction of old human lenses. Methods. The high molecular weight aggregate and lower molecular weight fra ctions were prepared from water soluble proteins of old human lenses. Synth etic peptides corresponding to expected amidated and deamidated tryptic fra gments of gammaS crystallin, together with reverse phase chromatography, we re used to resolve and quantitate possible deamidation of glutamine-92, glu tamine-96 and asparagine-143 from this protein. Results. Analyses of the high molecular weight aggregate from lenses of dif ferent ages consistently demonstrated deamidation of asparagine-143, with n o deamidation of glutamine-92 or glutamine-96, while analyses of the lower molecular weight fraction from the same lenses showed no detectable deamida tion of any of these three residues. Conclusions. Preferential deamidation of asparagine-143 of gammaS crystalli n is present in the high molecular weight fraction of human lenses, consist ent with the possibility that modification of this residue may play a role in the aggregation process occurring in vivo.