title: Topography of tyrosine residues and their involvement in peroxidation of polyunsaturated cardiolipin in cytochrome c/cardiolipin peroxidase complexes.
abstract: Formation of cytochrome c (cyt c)/cardiolipin (CL) peroxidase complex selective toward peroxidation of polyunsaturated CLs is a pre-requisite for mitochondrial membrane permeabilization. Tyrosine residues - via the generation of tyrosyl radicals (Tyr) - are likely reactive intermediates of the peroxidase cycle leading to CL peroxidation. We used mutants of horse heart cyt c in which each of the four Tyr residues was substituted for Phe and assessed their contribution to the peroxidase catalysis. Tyr67Phe mutation was associated with a partial loss of the oxygenase function of the cyt c/CL complex and the lowest concentration of H(2)O(2)-induced Tyr radicals in electron paramagnetic resonance (EPR) spectra. Our MS experiments directly demonstrated decreased production of CL-hydroperoxides (CL-OOH) by Tyr67Phe mutant. Similarly, oxidation of a phenolic substrate, Amplex Red, was affected to a greater extent in Tyr67Phe than in three other mutants. Tyr67Phe mutant exerted high resistance to H(2)O(2)-induced oligomerization. Measurements of Tyr fluorescence, hetero-nuclear magnetic resonance (NMR) and computer simulations position Tyr67 in close proximity to the porphyrin ring heme iron and one of the two axial heme-iron ligand residues, Met80. Thus, the highly conserved Tyr67 is a likely electron-donor (radical acceptor) in the oxygenase half-reaction of the cyt c/CL peroxidase complex.
authors.affiliation: Center for Free Radical and Antioxidant Health, Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Alexandr A
authors.initials: AA
authors.lastname: Kapralov
authors.forename: Naveena
authors.initials: N
authors.lastname: Yanamala
authors.forename: Yulia Y
authors.initials: YY
authors.lastname: Tyurina
authors.forename: Laura
authors.initials: L
authors.lastname: Castro
authors.forename: Alejandro
authors.initials: A
authors.lastname: Samhan-Arias
authors.forename: Yuri A
authors.initials: YA
authors.lastname: Vladimirov
authors.forename: Akihiro
authors.initials: A
authors.lastname: Maeda
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Weitz
authors.forename: Jim
authors.initials: J
authors.lastname: Peterson
authors.forename: Danila
authors.initials: D
authors.lastname: Mylnikov
authors.forename: Verónica
authors.initials: V
authors.lastname: Demicheli
authors.forename: Verónica
authors.initials: V
authors.lastname: Tortora
authors.forename: Judith
authors.initials: J
authors.lastname: Klein-Seetharaman
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D000818:Animals; D002308:Cardiolipins / Q000737:chemistry*; D003198:Computer Simulation; D045304:Cytochromes c / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000737:chemistry; D006736:Horses; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051336:Mitochondrial Membranes / Q000378:metabolism; D009154:Mutation; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry; D010105:Oxygenases / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry; D010544:Peroxidases / Q000737:chemistry*; D010649:Phenylalanine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D002308:Cardiolipins; D014443:Tyrosine; D006418:Heme; D010649:Phenylalanine; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D007501:Iron; D010544:Peroxidases; D009195:Peroxidase; D010105:Oxygenases; D010100:Oxygen