BIOL 2P03 Lecture Notes - Lecture 9: Tomm22, Intermembrane Space, Hspa8

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Boil 2p03 Making Organelles
Lecture 9
1. Making Organelles in Mitochondria
Building mitochondria and the oxphos machinery
Mito proteins include
Mito localizing sequences are usually at N-terminus
-TCA cycle enzymes -Substrate transporters -Fatty acid catabolism
-NADH shuttles -ATP/ADP shuttles
Some functional mito proteins (eg. respiratory complexes) have 30 or more
subunits, including encoded by mtDNA and others by nuclear DNA
1. mtDNA encoded subunits are transcribed and translated in the matrix on
mitochondrial ribosomes
2. nuclear DNA encoded subunits are made on cystolic ribosomes & imported
How are nuclear encoded proteins imported into the mitochondria
Challenge-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 them
2. recognized by import apparatus
3. brought into the mitochondria
4. end up in the right place
5. often also processed (N-terminal targeting sequence is removed
6. refolded into functional 3D conformation
7. assemble into multimeric complexes
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