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Oxidative stressVadim Gladyshev
Redox Biology Center, University of Nebraska
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Origin of oxidative stress
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Formation of earth: ~4.5 billion years
Chemical evidence of life on earth : ~3.85 billion years ago
Initially, the Earth had a reducing environment
- Gaseous mixtures of NH3, CH4, H2O, H2
- No molecular oxygen, excess metals
Oxygen is a potent oxidant- Easy transfer of electrons to oxygen - Oxidative metabolism (respiration)
Oxygen toxicity and reduced solubility of metals
Redox Biology and the Evolution of Life
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Utilization of Oxygen by Organisms
All animals and plants (and ancestral eukaryote) use oxygen to
generate energy
2~3 billion years ago, probably due to the evolution of oxygen-
evolving photosynthetic organisms
A prevalent element (53.8% atomic abundance in the earth’s crust,
21% in atmosphere)
Oxygen is soluble in pure water (surface water is generally in
equilibrium with the atmosphere)
However, diffusion of oxygen through tissues is very low (evolution of
oxygen transfer mechanism)
Intermediates of oxygen metabolism are also utilized for physiological
purposes (e.g. signaling).
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Oxidative stress
High Low
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Oxygen Toxicity
Generation of reactive oxygen species
A free radical is any species capable of independent existence
that contains one or more unpaired electrons
Sources of oxygen free radicals (reactive oxygen species)
- Mitochondrial electron transport chain
- Transition metal-mediated reactions
- Designated systems for ROS generation
Reactive oxygen species-mediated reactions
Moderately or highly reactive
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Fe2+ (Cu+) + H2O2 <-> HO. + HO- + Fe3+ (Cu2+)
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Neutrophil-mediated killing of bacteria
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Adaptations to Oxygen Toxicity
Anaerobic life
Defense mechanisms against oxygen toxicity
Prevention of generation of reactive oxygen species
- Metal sequestration
Antioxidants and antioxidant enzymes
- Scavenge reactive oxygen species
Damage repair systems
- DNA and protein damage repair
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Cu Zn Superoxide Dismutase
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Catalase
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Peroxiredoxin
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Signaling by hydrogen peroxide
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Oxidation of Cys residues as the basis for peroxide signaling
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Nitric Oxide
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CO is an important regulator of hypoxic sensing by the carotid body
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Are antioxidants effective in human health and disease?
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Among proteins with functional Cys, some utilize this residue for redox catalysis:
thiol oxidoreductases
MsrA MsrB fRMsr
TRX GRX
variety of unrelated
folds
Thiol oxidoreductases
The main fold:Thioredoxin fold
(3 layers, a/b/a; mixed beta-sheet of 4 strands, order 4312)
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Thiol oxidoreductases - catalytic and resolving Cys residues
PDI MsrB1 fRMsr 1-Cys Prx
Two types of redox active Cys: Catalytic Cys (k) and Resolving Cys (r)
Different organization of resolving Cys in thiol oxidoreductases
kk
kr
kr
r
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Selenocysteine (Sec) in proteins: Sec is always placed in the active site, and it serves the function of the catalytic redox Cys
Fomenko et al (2007)
Thiol oxidoreductases: catalytic Cys and Sec
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Involved in many biochemical processes and play central roles in redox homeostasis
Thiol oxidoreductases - functions
Thioredoxin system: TRXs, TR..
Glutathione/Glutaredoxin system: GRXs, GR..
Removal of ROS: AhpC, PRXs..
Met oxidative stress repair: MsrA, MsrB ..
Formation of disulfide bonds: Dsbs, Ero1, PDI …
V ≈ -250 mV
V ≈ -150 mV
Structure / AA composition around catalytic Cys: Modulation of pKa and Redox potential
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+
Normal
Apoptotic
Cys modificationsTrans-nitrosylation: effects on apoptotic pathways
GSNO-protein AND protein-protein interaction Specificity
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Trace elements (micronutrients)
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GTP
Precursor Z
Molybdopterin
(MPT)
Mo-MPT
(Moco)
Nitrogenase (Fe-Mo)
ModABC
WtpABC
TupABC
MOT1
Molybdenum (Mo)
- Prokaryotes
- Eukaryotes
Sulfite oxidase (SO)
Xanthine oxidase (XO)
Dimethylsulfoxide reductase (DMSOR)
Aldehyde:ferredoxin oxidoreductase (AOR)
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Chicken sulfite oxidase
Sulfite oxidase active site
3D structure
(PDB code: 1SOX)
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Copper (Cu)
- Prokaryotes
Cytochrome c oxidase subunit I (COX I)Cytochrome c oxidase subunit II (COX II)Plastocyanin family
Azurin familyRusticyanin (RC)Nitrosocyanin (NC)Nitrous oxide reductase (N2OR)NADH dehydrogenase 2 (NDH-2)
[Cu,Zn] superoxide dismutase (CuZn SodC)Copper amine oxidase (CuAO)
Particulate Methane monooxygenase (pMMO)
Multicopper oxidases (MCOs)
NiR, CueO, laccase, bilirubin oxidase, etc.
Tyrosinase
CopA
CutCCutF
CusCBA
CusF
CtaA (Cyanobacteria)
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Ctr1
ATP7
CutC?
[Cu,Zn] superoxide dismutase (CuZn SodC)Copper amine oxidase (CuAO)Multicopper oxidases (MCOs) Laccase, Fet3p, hephaestin, ceruloplasmin, etc.
Plantacyanin (PNC)
Umecyanin, mavicyanin, stellacyanin, etc.
Peptidylglycine alpha-hydroxylating monooxygenase (PHM)Dopamine beta-monooxygenase (DBM)HemocyaninCnx1GGalactose oxidase (GAO)
- Eukaryotes
Cytochrome c oxidase subunit I (COX I)Cytochrome c oxidase subunit II (COX II)Plastocyanin family
Tyrosinase
Copper (Cu)
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ATPADP
Cu(I)
CusCBA
CusF
Cu(I)
Ndh2
Cu(II)
Cu(I)
CueOCu(I)
Cu(II)
Cu(I) or Cu(II)
CopA
CutC?
CutF
?
?
?
?
CopZ
COX
Blue copper proteins
Cu homeostasis in bacteria
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Cu homeostasis in eukaryotes
Ctr1A
TP
7Me
tallo
thio
ne
ins
Atx1
ATP7
Golgi
CCS chaperone
Cu-Zn SOD
Cox17
Sco1
Mitochondrion
COX
Cox11
Cu ion
Nucleus
Tyrosinase
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Human Cu-Zn SOD
copper (blue-green sphere) and zinc (grey spheres)(PDB code: 1HL5)
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Nickel (Ni) and cobalt (Co)
Urease
Ni-Fe hydrogenase
Carbon monoxide dehydrogenase (Ni-CODH)
Acetyl-coenzyme A decarbonylase (CODH/ACS)
Ni-containing superoxide dismutase (SodN)
Methyl-coenzyme M reductase (MCR)
Nik/CbiM
Nik/CbiN
Nik/CbiQ
Nik
/Cb
iO
Nik/CbiMNQO (Nik/CbiKMLQO)
Nik/CbiL
Nik/CbiK
Nik/CbiM
Nik/CbiQ
Nik
/Cb
iO
NikB
Nik
D
NiK
A NikC Nik
E
NikABCDE
HupE/UreJ
NiCoT
UreH
Vitamin B12
(cobalamin)
B12-dependent isomerase - Methylmalonyl-CoA mutase (MCM)
- Isobutyryl-CoA mutase (ICM)
- Glutamate mutase (GM)
- Methyleneglutarate mutase (MGM)
- D-lysine 5,6-aminomutase (5,6-LAM)
- B12-dependent ribonucleotide reductase II
- Diol/glycerol dehydratase (DDH/GDH)
- Ethanolamine ammonia lyase (EAL)
B12-dependent methyltransferase - B12-dependent methionine synthase (MetH)
- B12-dependent methyltransferases
Mta, Mtm, Mtb, Mtt, Mts, Mtv and Mtr
B12-dependent dehalogenase
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Overview of trace Overview of trace element utilizationelement utilization
• Cu utilization is widespread in bacteria and eukaryotes, but restricted in archaea
• Only a few organisms utilize all five trace elementsBacteria: 94Archaea: 3Eukaryotes: 9
• >50% prokaryotic organisms use the four metals
• Only 9 eukaryotes use the four metals
• Many Saccharomycotina lost the ability to use most of the five trace elements
Cu Ni Co (B12) Mo Se (Sec)Phyla
Total 432(80%) 319(59%) 410(76%) 401(74%) 139(26%)
Total 26(55%) 39(83%) 45(96%) 46(98%) 6(13%)
Total 154(96%) 51(32%) 49(31%) 105(66%) 76(48%)
Bacteria
Archaea
Eukarya
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Fungi MetazoaViridiplantae
• Land plants possess the largest Mo- and Cu-dependent metalloproteomes in eukaryotes
Metalloproteomes and selenoproteomes in eukaryotesMetalloproteomes and selenoproteomes in eukaryotes
Co(B12)
Se(Sec)
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Are antioxidants effective in human health and disease?