Structural features of isomerizable aspartyl residues in human ?-crystallins.

ABSTRACT: PURPOSE: The aspartyl (Asp) residues 58 and 151 in ?A-crystallin, and Asp36 and Asp62 in ?B-crystallin in human lenses are known to be highly isomerized with aging. We investigate structural environments of these isomerizable aspartyl residues in ?-crystallins of human lenses. METHODS: To perform limited proteolysis experiments of purified human ?A- and ?B-crystallins, endoproteinase Asp-N (EC 3.4.24.33), which selectively cleaves the peptide bonds at the amino side of aspartyl and cysteic acid residues, was employed. By proteolysis approach coupled with the time-of-flight mass spectrometry (TOF-MS) method, we determined the cleavage points along protein sequences. RESULTS: Proteolysis by endoproteinase Asp-N occurred preferentially at the site of isomerizable aspartyl residues in ?A- and ?B-crystallins. CONCLUSIONS: It is found that isomerizable aspartyl residues in ?-crystallins in human lenses were located not only in the solvent accessible area but also at regions displaying inherent conformational flexibility.

SUBMITTER: Shimizu K 

PROVIDER: S-EPMC3398496 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature