Intracellular Compartments and Protein Sorting II Flashcards
What type of gene makes up mitochondrial proteins?
Nuclear genes
Where can the TOM take cargo in general?
From cytosol to IMS or Outer membrane
Where can TIM take cargo in general?
From IMS to matrix or inner membrane
Where is the receptor for the sorting sequence located in the mitochondria?
It is part of the translocase complex
What are the four distinct compartments of the mitochondria?
OM, IMS, IM, Matrix
How do proteins enter the mitochondria and what helps them?
Proteins enter the mitochondria unfolded with the help of HSP 40 and HSP70
How are TOM supportive of the endosymbiosis theory?
The pore is a Beta barrel which is usually seen in prokaryotes
What is the significance of SAM?
SAM or TOB inserts beta barrels into the outer membrane AFTER they go through TOM.
What is the significance of MIM?
MIM can interact with SAM and inserts transmembrane alpha helical proteins after they go through TOM
Where is the sorting sequence for B-barrel proteins and does it get cleaved?
The sorting signal is a B-Signal found on the first beta strand inserted into SAM, it does not get cleaved after insertion into Outer membrane.
For alpha helices what are the sorting signals and do they get cleaved?
They are signal anchor domains with hydrophobic amino acids and a positive charge at the N terminus and they do not get cleaved after insertion into the outer membrane
Where are signal anchor domains found on transmembrane alpha helices?
Can be on the N terminal or Internal.
If N terminal MIM is used
If internal SAM is used
Can be single pass or multi pass.
Single=MIM or SAM depends on location of signal
Multi= MIM and TOM70What are the chaperones in the IMS?
Small TIMs
What does MIA do?
Reduces proteins rich in Cysteine
Differentiate TIM23 and TIM22.
TIM23 is the workhorse it inserts most of the IM transmembrane proteins.
TIM22 inserts some metabolite carriers as well as TIM23
What are the three pathways to get to the Inner Membrane?
- TOM–> TIM23 the sequence is cleaved
- TOM—> TIM22 uses small TIM chaperones
- OXA for proteins made in the matrix to inner membrane
What is the sorting sequence to get into the matrix of the mitochondria?
Amphipathic helix- also gets cleaved after import needs energy (ATP)
What helps fold proteins inside the matrix?
HSP 60
How are proteins entered into the ER from Cytosol?
Unfolded through Co-Translational insertion or Post-Translational insertion.
What is Co-Translational insertion for Cytosol to ER?
Happens on the RER, Needs a SRP, SRP receptor, and Sec61 gated translocator
What is Post-Translational insertion Cytosol to Er?
Happens on free ribosome, Needs Cytosolic chaperon proteins, Sec61 gated translocator, and BiP.
Where is the sorting sequence for proteins entering the ER?
Located on the N terminus- cleaved by signal peptidase.
N domain is hydrophillic and charged
H domain is hydrophobic (most important)
C domain is polar
Where does energy use occur during Co-Translational Insertion?
During SRP recycling and translation elongation
Where does energy use occur during post translational insertion?
When the binding protein is pulling (BiP)
