The Spontaneous Amino-acid Modifications and Those Contributions for the Aged Lens Proteins

Abstract

Highly concentrated crystalline family is correctly folded and packed to maintain transparency in lens. On the other hand, lens does not have turn over function. Therefore, spontaneous post-translational modifications, such as deamidation and isomerization are accumulated during a life. In this study, we focused on the distribution and contribution of deamidation and isomerization in lens crystalline. The distributions of each of modification were screened by conventional and non-conventional mass spectrometry. In order to predict the contribution of site-specific modification, each of target amino acid in crystalline was replaced by deamidated ones, or various other amino acid using site directed mutagenesis. Each of recombinant crystalline was expressed by E.coli. Those crystalline biophysics were compared with wild type crystalline. Those results showed the distributions of modification are different depending on crystalline oligomer states or crystalline solubility in aged lens. The result suggested that the modifications in crystalline would induce abnormal subunit-subunit interaction, and reduce stability in aged lens. This implied one reason for senile cataract formation in aged lens via spontaneous post-translational modification in crystallines.