Mitochondria

Dr. S. Subba Tata
M.Sc., M.Sc., M.Tech., Ph.D.
Assistant Professor (C)
Department of Botany, Andhra University
MITOCHONDRIA

KOLLIKER - 1850
MITOCHONDRIA were first observed as granular structures in
the striated muscles

25 percent of the volume of the cytoplasm
Mature red blood cells - no Mitochondria
Popularly called POWERHOUSE OF THE CELL
MITOCHONDRIA
Carl Benda - 1898 - proposed – Mitochondria
mitos (thread) and chondrion (granule)

Present in all eukaryotic cells
Uniform distribution in the cytoplasm
Restricted distribution in many cells
Mitochondria with many cristae - mechanical and osmotic
work situations
 Muscle fibres
 Kidney tubule cells
 Rod and Cone cells of retina
Many large mitochondria - Sarcosomes - Myocardial
muscle cells
Localization

Number
Amoeba – 50,000
Eggs of sea urchin – 1,40,000 to 1,50,000
Oocytes of amphibians – 3,00,000
Liver cells of rat - 500 to 1600
Morphology
Shape
Filamentous
Granular
Club
Racket
Vesicular
Ring
Round
Size
Length : ~ 1-2μm
Width : ~ 0.1-0.5μm

STRUCTURE
Palade’s model
Infolding or ‘Baffle’ model
PALADE - 1952
Crista junction model
SJOSTRAND - 1953
Lea et al., 1994; Mannella et al., 1994

* Monoamine oxidase, rotenone-insensitive NADH-cytochrome-C-reductase,
kynurenine hydroxyalase and fatty acid CoA ligase *
Outer Membrane (OM)

hTom40 forms the pore of the translocase
hTom20, hTom22 and hTom70 function as receptors
hTom22 plays an additional role in the assembly of the complex
hTom5, hTom6 & hTom7 - small TOMs- regulate the dynamics and
assembly of the complex
Translocase of Outer Membrane
- serves as a general protein entry gate -

Sorting and Assembly Machinery
- serves to insert the proteins into the outer membrane -
hSam40 is a core protein of this complex – Insertion activity
MTX1 & MTX2 (Metaxins) – Protein sorting activity

Inner Membrane (IM)
Inner Membrane (IM)
IBM CM
Tubular Spherical Triangular Wavy Lamellar Strap

Translocase of
Inner Membrane
- serves to insert the proteins
into the inner membrane -
hTim22 forms the pore of
translocase
hTim29 function as receptor and
mediates the formation of complex
 AGK (Acylglycerol kinase) –
Lysophosphatidic acid (shows
growth factor like activity)

Mitochondrial Intermembrane Assembly
- serves to assemble the proteins in the intermembrane space by
catalyzing the disulfide bonds -
hMia40 is a core protein of this complex – Assemble & disulfide bonds
AIF – Apoptosis Inducing Factor
ALR – Augmenter of Liver Regeneration – Mitochondrial Biogenesis

Translocase of Inner Membrane
- serves to insert the proteins into the inner membrane and to
transfer the proteins into the matrix -
hTim23 and hTim17 forms the pore of translocase
hTim50 function as receptor
Import motor – helps to translocate the proteins into the matrix

Multi – Subunit Complex
- serves to stabilize the Cristae-
Mic60 is a core protein of this complex
MICOS – intern to associates with SAM complex to form MIB for the
stability of both the membranes

Inner Membrane (IM)
Nicotinamide adenine dinucleotide dehydrogenase (NADH)
Flavin adenine dinucleotide dehydrogenase (FADH)
Diphosphopyridine nucleotide dehydrogenase (DPNH)
ATP synthetase
Succinate dehydrogenase
β-hydroxybutyrate dehydrogenase
Carnitive fatty acid acyl transferase
Four cytochromes (Cyt. b, Cyt. c, Cyt.c1, Cyt. a and Cyt. a3)
Ubiquinone or coenzyme Q10
Non-heme copper and iron

 Inner membrane proteins
 Oxidative phosphorylation
 Metabolite exchange
 Protein translation
 Protein translocation
 Protein degradation
 Iron/Sulfur cluster biogenesis
 Mitochondrial morphology
CM
Oxidative phosphorylation
Iron/Sulfur cluster biogenesis
Protein synthesis
Transport of mtDNA-encoded proteins
Proteins involved in mitochondrial fusion
Protein transport of nuclear-encoded proteins
IBM

 consists a complex mixture of
enzymes - for the oxidation of
pyruvate and fatty acids and for
the citric acid cycle and for
expression of mitochondrial
genes
Ribosomes
tRNAs
DNA
Oxygen, Carbon dioxide and
other recyclable intermediates
Matrix

 Adenylate kinase
 Nucleoside diphosphokinase
Intermembrane space

 Produce energy
 Storage tank of calcium ions
 Building of certain parts of the blood and hormones
(e.g. testosterone and estrogen)
Detoxification of ammonia
Participates in diverse cellular process like: immune
responses ; mitophagy ; stress signalling and apoptosis
Functions

Mitochondria Biogenesis
Mitochondrial fission
- Mitochondria reproduction -
Drp1 : Dynamin related protein 1
Fs1 : Fission protein 1
Mff : Mitochondrial protein factor 1
Mid49: Mitochondrial dynamics protein 49
Mid51: Mitochondrial dynamics protein 51

DYNAMIN RELATED PROTEIN 1
 Mechanochemical enzyme
 4 domains - Tertiary structure
 Contains – 736 amino acids
 Molecular weight – 81.6kDa

1
2 3 4
1 : Fission protein 1
2 : Mitochondrial protein factor 1
3 : Mitochondrial dynamics protein 49
Mitochondrial fission

1
2 3 4
1 : Fission protein 1
2 : Mitochondrial protein factor 1

 Circular ds DNA
 16,569bp – hMt DNA
 Outer stand – Heavy
 Inner strand – Light
 Both strands acts as non
coding strands (HSP1 & HSP ;
LSP)
 Each strand possess one Ori
for replication
 Only one non – coding DNA
region identified - D- loop
(~1kbp)
 Contains 37 genes
 Protein coding genes – 13
ND1; ND2; ND3; ND4;
ND4L; ND5 & ND6 of
complex – I (7/43)
Cyt b of complex –III (1/11)
COXI; COXII & COXII of
complex – IV(3/13)
ATPase6 & ATPase8 of
complex –V(2/16)

Ribosomal RNA coding
genes – 2
 12S RNA
 16S RNA
 tRNA coding genes – 22
Heavy Strand
T D
L W
S M
H I
R L
G V
K F
Light Stand
P C
E N
S A
Y Q

Mitochondria

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