Intracellular Compartments And Protein Sorting 2 Flashcards
Movement of proteins into the mitochondria is called ______
Translocation
______ direct proteins to correct compartment in mitochondria
Signal Sequences
Mitochondrial Signal sequences
- N-terminal and internal signal sequences
- Positively charged residues cluster on one end and hydrophobic on the other end of the helix
( note that specific receptor proteins recognize this configuration rather than precise sequence)
Multi-subunit protein complexes called ______ mediate translocation (movement of protein into mitochondria)
Protein translocators
Translocase of the outer membrane (TOM) is present in the ______ membrane
Outer
Which Translocase is required for import of all nuclear encoded proteins into the mitochondrial membranes
Translocase of the outer membrane (TOM)
Translocase of the inner membrane (TIM) is present in what membrane
Both outer and inner membrane
Most mitochondrial proteins are encoded in _____. Synthesized on ____ and _____
Nuclear DNA, synthesized on ribosome and imported into mitochondria
What are the two TIM complexes
TIM 22 and TIM23
TIM23 transports _____ and helps insert membrane proteins _______
soluble protein into matrix, in inner membrane
TIM 22 mediates the insertion of _____
a specific subclass of proteins (e.g. ATP, ADP and Pi transporter)
TOM and TIM complexes have 2 components
- Receptors for mitochondrial precursor proteins
- Translocation channels
SAM complex (sorting and assembly machinery)
- Translocates and inserts/folds beta barrel proteins in the outer membrane
OXA complex
- Mediates insertion of proteins synthesized in mitochondria
What are the translocators in the mitochondrial membranes
- TOM and TIM complexes
- SAM complex
- OXA complex
Precursor proteins enter the mitochondria are ____
unfolded
The unfolding of precursor mitochondrial proteins is maintained by interactions with
chaperone proteins (cytosolic Hsp 70 family)
Import receptors of TOM complex bind _____ of incoming protein. Then chaperone proteins are ____ and unfolded protein is fed- _____ first into the transaction channel
signal sequence, stripped off, signal sequence
TOM transports protein across the outer membrane to the _______. Then protein binds to _____ complex and moves through channel to matrix and then the signal sequence is cleaved off by
inner membrane space, TIM complex, peptidase
Bound Hsp 70 dissociate from precursor mitochondrial at expense of
ATP hydrolysis outside the mitochondria
After passing through TOM, protein interacts with TIM and transport through TIM depends upon _____
membrane potential
Energy in electrochemical gradient drives translocation of positively charged sequence through TIM by _____
electrophoresis
______ bound to TIM23 on matrix side and pulls protein into matrix space
Mitochondrial Hsp 70
The release of protein, by Hsp70, in the matrix space is an
ATP dependent step
____ helps in folding of imported mitochondrial protein using ATP
Hsp60
import of mitochondrial proteins into the outer membrane
- Pass through TOM complex and enter inter-membrane space
- Bind to chaperone proteins
- Then bind to SAM complex in outer membrane
- SAM inserts and folds them in outer membrane (ex. porins(beta barrel proteins))
ER is organized into a network of _______ and ____
branching tubules and sacs
ER membrane continuous with ______
nuclear membrane
Internal space of ER called ______
ER lumen
ER plays central role in ___ and ____
protein and lipid synthesis
What is the site of production of all TM proteins
ER
What is co-translation
The ER-bound ribosome forms protein
