Specific glutamine and asparagine residues of gamma-S crystallin are resistant to in vivo deamidation

It has been hypothesized that resistance to nonenzymatic deamidation of asp aragine and glutamine residues may be an important determinant of protein s tability in vivo, As a test of this hypothesis, we analyzed the central reg ion of old human lenses, which contain proteins such as gamma-S crystallin that were synthesized during the fetal-embryonic periods of development. To tal protein from the fetal embryonic region of old human lenses was digeste d with trypsin, followed by resolution of tryptic fragments containing amid ated and deamidated forms using high pressure liquid chromatography-reverse phase chromatography together with synthetic peptide standards and mass sp ectral analysis. The results demonstrate no detectable deamidation of gluta mine 92, glutamine 96, asparagine 143, and glutamine 170 from gamma-S cryst allin from old human lenses, consistent with the hypothesis that very long- lived pro proteins can contain asparagine and glutamine residues that are e xtremely resistant to in vivo deamidation.