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Lecture 9

BIOL 2P03 Lecture Notes - Lecture 9: Signal Peptide, Nuclear Dna, Autophagy


Department
Biological Sciences
Course Code
BIOL 2P03
Professor
Jeff Stuart
Lecture
9

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Lecture 9 Making organelles
1. Mitochondria
2. Chloroplasts
Building mitochondria and the oxphos machinery
13 mtDNA proteins
1000-1500 proteins per mitochondrion
Mito proteins include: TCA cycle enzymes, substrate transporters, fatty acid
catabolism, NADH shuttles, ADP/ATP shuttles, parts of various synthetic
pathways
Some functional mito proteins (e.g. respiratory complexes) have 30 or more
subunits, including subunits encoded by mtDNA and others by nuclear DNA
Synthesis of respiratory complexes – how are they made?
(1) mtDNA encoded subunits are transcribed and translated in matrix on
mitochondrial ribosomes
(2) nuclear DNA encoded subunits are made on cytosolic ribosomes & imported
Proteins are big:
The inner membrane must maintain its integrity to maintain the proton
gradient
Solution:
Many proteins are involved in the regulated import of mitochondrial proteins
while maintaining proton gradient
Mitochondrial proteins made in the cytosol must be:
(1) Unfolded
Heat shock proteins (aka chaperonins) help to unfold proteins
(2) Recognized by import apparatus
(3) Brought into mitochondria
(4) End up in the right place (matrix, inner membrane, inter-membrane space,
outer membrane)
Mitochondrial proteins made in the cytosol must be:
(1) Unfolded
(2) Recognized by import apparatus
(3) Brought into mitochondria
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