Intramolecular oxidation of cytochrome c by covalently attached sulfoaromatic molecules.
Two photosensitive molecules, 1-maleimidopyrene-3,6,8-trisulfonate (MPTS) and N-acetylaminoethyl-1-aminonaphthalene-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 photoinduced electron-transfer reaction from the ferros heme group to the oxidized dyes. The rate constant was found to be (3.6 +/- 0.4) x 10(4) 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.
Kotlyar
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Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel. sasha@hemi.tau.ac.il
Borovok
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D001190:Arylsulfonates / Q000737:chemistry; D003574:Cytochrome c Group; D005296:Ferrous Compounds / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D008301:Maleimides / Q000737:chemistry*; D009282:Naphthalenesulfonates; D010084:Oxidation-Reduction; D010777:Photochemistry; D011721:Pyrenes / Q000737:chemistry*; D012996:Solutions; D013057:Spectrum Analysis; D014867:Water
C109368:1-maleimidopyrene-3,6,8-trisulfonate; D001190:Arylsulfonates; D003574:Cytochrome c Group; D005296:Ferrous Compounds; D008301:Maleimides; D009282:Naphthalenesulfonates; D011721:Pyrenes; D012996:Solutions; D014867:Water; D006418:Heme; C048876:1,5-AEDANS; C005047:pyranine