title: Structural re-arrangement and peroxidase activation of cytochrome c by anionic analogues of vitamin E, tocopherol succinate and tocopherol phosphate.
abstract: Cytochrome c is a multifunctional hemoprotein in the mitochondrial intermembrane space whereby its participation in electron shuttling between respiratory complexes III and IV is alternative to its role in apoptosis as a peroxidase activated by interaction with cardiolipin (CL), and resulting in selective CL peroxidation. The switch from electron transfer to peroxidase function requires partial unfolding of the protein upon binding of CL, whose specific features combine negative charges of the two phosphate groups with four hydrophobic fatty acid residues. Assuming that other endogenous small molecule ligands with a hydrophobic chain and a negatively charged functionality may activate cytochrome c into a peroxidase, we investigated two hydrophobic anionic analogues of vitamin E, α-tocopherol succinate (α-TOS) and α-tocopherol phosphate (α-TOP), as potential inducers of peroxidase activity of cytochrome c. NMR studies and computational modeling indicate that they interact with cytochrome c at similar sites previously proposed for CL. Absorption spectroscopy showed that both analogues effectively disrupt the Fe-S(Met(80)) bond associated with unfolding of cytochrome c. We found that α-TOS and α-TOP stimulate peroxidase activity of cytochrome c. Enhanced peroxidase activity was also observed in isolated rat liver mitochondria incubated with α-TOS and tBOOH. A mitochondria-targeted derivative of TOS, triphenylphosphonium-TOS (mito-VES), was more efficient in inducing H2O2-dependent apoptosis in mouse embryonic cytochrome c(+/+) cells than in cytochrome c(-/-) cells. Essential for execution of the apoptotic program peroxidase activation of cytochrome c by α-TOS may contribute to its known anti-cancer pharmacological activity.
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health.
authors.forename: Naveena
authors.initials: N
authors.lastname: Yanamala
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Kapralov
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health.
authors.forename: Mirjana
authors.initials: M
authors.lastname: Djukic
authors.affiliation: the Departments of Environmental and Occupational Health.
authors.forename: Jim
authors.initials: J
authors.lastname: Peterson
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health.
authors.forename: Gaowei
authors.initials: G
authors.lastname: Mao
authors.affiliation: the Division of Metabolic and Vascular Health, Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom.
authors.forename: Judith
authors.initials: J
authors.lastname: Klein-Seetharaman
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health.
authors.forename: Detcho A
authors.initials: DA
authors.lastname: Stoyanovsky
authors.affiliation: the Biomedical Research Center, University Hospital, Hradec Kralove 569810, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Stursa
authors.affiliation: the Institute of Biotechnology, Academy of Sciences of the Czech Republic, Prague 14220, Czech Republic, and the School of Medical Science, Griffith University, Southport, Queensland 4222, Australia.
authors.forename: Jiri
authors.initials: J
authors.lastname: Neuzil
authors.affiliation: From the Center for Free Radical and Antioxidant Health, the Departments of Environmental and Occupational Health, Pharmacology and Chemical Biology, Radiation Oncology, and Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260.
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006736:Horses; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018345:Mice, Knockout; D008958:Models, Molecular; D015394:Molecular Structure; D009195:Peroxidase / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013053:Spectrophotometry; D014815:Vitamins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D024502:alpha-Tocopherol / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D014815:Vitamins; C012552:alpha-tocopherol phosphate; D045304:Cytochromes c; D009195:Peroxidase; D024502:alpha-Tocopherol
keywords: Cancer Therapy; Computer Modeling; Cytochrome c; Peroxidase; Protein Folding; Vitamin E