An analysis of the H2O2-mediated crosslinking of lens crystallins catalyzed by the heme-undecapeptide from cytochrome c

Richard S. Bodaness, Maureen Leclair, J. Samuel Zigler

Research output: Contribution to journalArticlepeer-review

Abstract

In contrast to other tissues, the lens exists in a milieu containing relatively high (micromolar) concentrations of H2O2. It has been demonstrated that activation of H2O2 to more-potent oxidant species via the heme-undecapeptide from cytochrome c produces alterations in lens crystallin polypeptides similar to the changes found in cataract. These include crystallin polypeptide crosslinking and the development of a blue fluorescence not attributable to tryptophan. Of the three classes of mammalian crystallins, γ-crystallin is crosslinked by heme peptide-H2O2, whereas α and β are not. Hemepeptide plus H2O2 generates dityrosine from free tyrosine, and, concomitant with crosslinking, the γ-crystallin exposed to this system develops a new fluorophor with the characteristics of dityrosine. The findings with bovine and human crystallins are identical in this regard. In addition to the oxidation of tyrosine, exposure to heme peptide-H2O2 results in the oxidation of tryptophan. The intrinsic fluorescence of α, β, and γ-crystallins is due primarily to tryptophan, and the intrinsic fluorescence of each is decreased by heme peptide-H2O2. Thus, tryptophan oxidation occurs in all crystallins, but crosslinking occurs only in γ-crystallin and is associated with oxidation of tyrosine.

Original languageEnglish (US)
Pages (from-to)461-469
Number of pages9
JournalArchives of Biochemistry and Biophysics
Volume231
Issue number2
DOIs
StatePublished - Jun 1984

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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