Mitochondrium

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Mitochondrium Peroxisome - Chloroplast
Dr. habil. Kohidai László Assoc. Prof. Dept.
Genetics, Cell Immunobology Semmelweis
University 2008
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History

• Altmann describes Mch
• Benda - name Mitochondrium was given
  by him
• Warburg - invetigated the enzymes of
  respiratory chain
• Lehninger described oxydative
  phosphorylation

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Morphology
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Network of Mch in a fibroblast cell Detection of
ATP-syntase
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Characteristic data

• Size 7 x 0.5 mm
• BUT wide range in different cell types !
• Number depends on the energy requirements/budget
  of the cell
• sperim - 24
• WBC. - 300
• liver cell - 500-2500
• Chaos-Chaos - 500.000 !
• ameba

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Compositioncompartmentalisation

• Outer membrane
• poor in proteins
• characteristic protein porin
• (b-sheet trimers
• form channels)
• permeability up to 5000 dalton

• Inner membrane
• 70 proteins
• e- - transporter chaini
• ATP synthesis
• other point impermeable 20 cardiolipin

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• Matrix
• Pyruvate dehydrogenase complex
• Enzymes of citric acid cycle
• Enzymes of b-oxydation of fatty acids
• Enzymes of amino acid oxydation
• DNA, ribosomes
• ATP, ADP, Pi
• Mg2, Ca2, K

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Inner membrane of Mch
crista
tubular
fingerprint-like
berry-like
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Localization in the cell
Basal striation
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Mch as osmotic regulator of the cell
normal
condensed
Significant H20 ration of matrix moves to the
intermembraneous space and forms a condensed
comformation
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Relation of biochemical processes in Mch.
pyruvate
fatty acid
Acethyl-CoA
CO2
ATP
Citric acid cycle
NADHH FADH2
H2O
O2
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Terms of Chemiosmotic theory

• Mch. Respiratory chain moves electrons
• - pumps H into
  intermembrane space
• Mch. ATP synthase works also as a H pump.
• Reversible mechanism
• Several carrier molecules for metabolites, ions
  in the inner membrane of Mch.
• Other point of the inner membrane of Mch. is
  impermeable for H and OH-.

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1. NADH dehydrogenase
2. Succinyl dehydrogenase
3. Ubiquinone cytochrom c oxydoreductase
4. Cytochrom oxydase

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Enzyme systems of inner membrane in Mch
I.
e -
II.
III.
Acidic pH
H
IV.
Redox potential INCREASING I. lt III. lt IV.
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Resting phase
Matrix
H10-9 M
K Cl- 0.1 M
H10-9 M
Intermembrane space
Ionophore treated (Valinomycin)
H
Matrix
ATP
H10-9 M
KltCl-
H10-7 M
K
Intermembrane space
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Electrochemical proton-gradient
pH gradient
membrane-potential
DpH
DV
ATP synthesis
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NADH
NAD
NADH dehydrogenase
H
Q
b-c1 complex
cyt c
Electron transport in Mch
cytochrome oxydase
O2
H2O
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Knob-like protusions of the inner Mch membrane
ATP-synthase
proton carrier
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Structure of ATP-synthase
F1 ATP-ase (6 subunits)
Transmembrane H carriers (9 subunits)
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ATP-synthase
e - rotor a, b, d - stator
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Experimental evidence
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Bacterio-rhodopsin
ATP synthase
H
ADP Pi
H
H
H
H
H
ATP
H
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ATP
ADP Pi
H
ADP Pi
ATP
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Transports required by ATP-synthase
Symport
Antiport
Phosphate translocase
Adenine nucleotie translocase
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Brown adipose tissue Mch.
Heat
H
H
H
H
II.
I.
IV.
III.
thermogenin
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Transports
Signal seq.
! Hsp70 !
Receptor
Contact-point
Translocon GIP
Mch. Hsp-k
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Origin of Mitochondrion

• De novo synthesis
• Division
• Endosymbiont theory

Archaic Cyanobacteria 1.5 x 109 yrs ago

• porin (Gram (-) bact.)
• electron transport chain
• ATP synthase
• mt DNS
• ribosome

BUT Giardia has NO Mch (anaerob)
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Origin of Mitochondrion 2

• Composition of outer membrane eukaryotic type
  the inner membrane is composed by prokaryotic
  components
• Mch has own protein synthetic system, the starter
  amino acid is formyl-Met
• Inhibitors of protein synthesis in Mch
  antibiotics acting on bacterial protein synthesis

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Network of Mch in budding S. cerevisiae
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CELL PROLIFERATION
Isotope labelling
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mt-DNA

• ring shape, 5 10 copies/Mch.
• 20 Mch genes are coding proteins
• there are no introns
• few regulator genes
• no histons
• repliation, transcription, translation
• 22 tRNA, 2 rRNA

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Human mt-DNA
rRNA
Cyt b
ND1 2
ND3-6
I.
III.
II.
ATP-syntase
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Mch myopathy
Clusters of fibers
Single fibre
Crystalline structure in the matrix of Mch
Mass of pathologic Mch-s
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Peroxisome

• Single membrane coverage
• Selective import of proteins
• No genome
• Oxydative enzymes
• catalase
• urate oxydase (crystalloid)

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Origin of peroxisome

• O2 producing bacteria early phase of phylogeny
• the O2 is toxic to other cells/organisms
• peroxisome could neutralize the O2 and its
  radicals
• in the cytoplasm

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Functions of peroxisome

• RH2 O2 R H2O2 (toxic)
• H2O2 RH2 R 2H2O
• catalase (liver, kidney)
• b-oxydation alkyl chain - (C2 ac.CoA)n

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Peroxisomes in plants

• In plants
• leafs photorespiration - O2 consumption
  CO2
• germination glyoxylate cycle (glyoxysome)
• Fatty acid ac. CoA succinate
  glucose

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Peroxisome in plants
peroxisome
glyoxisome
lipid
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Peroxisome

• import of proteins

- 3 amino acid signal sequence on C-terminal -
PAF-1 peroxisomal assembly factor-1

• Zellweger syndrome
• protein to be impoted is affected

- empty peroxisomes
(brain, liver, kidney affected lethal)
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Gene transfection - Zellweger syndrome
PXR1
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Chloroplast
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Thylakoid membrane (light reaction)
Stroma (dark reaction)
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Engelmann-experiment (1894)
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Photopigments of chloroplast
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Z-scheme of electron transport in chloroplast
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Chloroplast NAPH / ATP synthesis
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Comparison of ATP generation in Mch - Chloroplast