title: Structural features of isomerizable aspartyl residues in human α-crystallins.
abstract: OBJECTIVE
  The aspartyl (Asp) residues 58 and 151 in αA-crystallin, and Asp36 and Asp62 in αB-crystallin in human lenses are known to be highly isomerized with aging. We investigate structural environments of these isomerizable aspartyl residues in α-crystallins of human lenses.
  
  
  METHODS
  To perform limited proteolysis experiments of purified human αA- and αB-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 αA- and αB-crystallins.
  
  
  CONCLUSIONS
  It is found that isomerizable aspartyl residues in α-crystallins in human lenses were located not only in the solvent accessible area but also at regions displaying inherent conformational flexibility.
authors: Research Reactor Institute, Kyoto University, Kumatori, Sennan, Osaka, Japan.
authors: Ken-ichi
authors: K
authors: Shimizu
authors: Akiko
authors: A
authors: Kita
authors: Noriko
authors: N
authors: Fujii
authors: Kunio
authors: K
authors: Miki
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D003545:Cysteine / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli; D006801:Humans; D007536:Isomerism; D007908:Lens, Crystalline / Q000378:metabolism* / Q000473:pathology; D008666:Metalloendopeptidases / Q000378:metabolism; D008969:Molecular Sequence Data; D059748:Proteolysis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D038202:alpha-Crystallin A Chain / Q000737:chemistry* / Q000235:genetics; D038203:alpha-Crystallin B Chain / Q000737:chemistry* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D038202:alpha-Crystallin A Chain; D038203:alpha-Crystallin B Chain; D001224:Aspartic Acid; D008666:Metalloendopeptidases; C058921:endoproteinase Asp-N; D003545:Cysteine