Intramolecular oxidation of cytochrome c by covalently attached sulfoaromatic molecules

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Abstract

Two photosensitive molecules, 1-maleimidopyrene-3,6,8-trisulfonate (MPTS) and N-acetylaminoethyl-1-aminonaphthalens-5-sulfonate (AEDANS), are employed to drive the intramolecular oxidation of the heme residue in cytochrome c. intense pulse illumination (60-120 MW cm-2) of MPTS and AEDANS in the aqueous solution by the third harmonic frequency of Nd-Yag laser drives a two successive-photon process of the dyes. The oxidized products originating from the dyes react with variety of electron donors. MPTS and AEDANS residues were covalently linked the Saccharomyces cerevisiae iso-1-cytochrome c by labeling of its single sulfhydryl group. When pulsed by intensive laser beam the heme of the labeled ferrocytochrome c undergoes fast oxidation. Transient absorption spectroscopy was used to directly measure the rate constants for the photoinduccd electron-transfer reaction from the ferros heme group to the oxidized dyes. The rate constant was found to be (3.6 ± 0.4) x 104 s-1 for MPTS derivative. The rate of the heme oxidation in AEDANS derivative was faster than response time of our detection system (20 ns). Rapid photooxidation of cytochrome c makes it a useful tool for Fast initiation of electron transfer in oxidized direction within complexes of cytochrome c with the other redox proteins.

Original languageEnglish
Pages (from-to)221-228
Number of pages8
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1321
Issue number3
DOIs
StatePublished - 20 Oct 1997

Keywords

  • Cytochrome c
  • Electron transfer
  • Photooxidation
  • Time-resolved spectroscopy

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