Protein Sorting for Mitocondria Transfer Flashcards
How many membranes do proteins need to cross for Mitochondrial Protein Import
2 Membranes
- Need to pass through the outer membrane, the inter-membrane space, and the inner membrane to reach the matrix
For proteins to be transported into the mitochondria, the protein must have…
A Signal Sequence on the N-Terminus
-The signal sequence is composed of positively charged amino acids such as lysines and arginines.
What recognizes the Signal Sequence?
An import receptor on the outer mitochondrial membrane
What is bound to the import receptor on the outer mitochondrial membrane?
A protein translocator
What can the import receptor and protein translocator do once the protein with the signal sequence is bound?
This complex can move along the outer membrane because the membrane is fluid. this complex will continue to move until it finds a contact site
Contact Site
when the linear protein within the outer membrane complex makes contact with another protein translocator on the inner membrane surface
Once the contact site is established what happens?
The linear polypeptide will move into the matrix with the help of ATP. The protein leaves the translocator
Once the linear polypeptide chain is in the matrix what will happen next?
Chaperone proteins help the polypeptide fold to its proper conformation. Then the signal sequence is cleaved.
Are proteins folded in the cytosol before import or in the mitochondrial matrix after transport?
Proteins are imported in a linear structure then folded in the mitochondrial matrix
Where is the single sequence on the mitochondrial matrix? Was this protein encoded in the mitochondrial DNA or nuclear DNA
The signal sequence is found on the N-Terminus
- Proteins is encoded from the Nuclear DNA
How does the mitochondria recognize incoming mitochondrial protein?
Signal Receptor
Where are the chaperones? What are their two main functions?
Chaperones are found in the Mitochondrial Matrix
FUCNTIONS
1. folding proteins
2. Prevent backsliding of proteins when they are in the translocators (They make sure to pull the protein into the matrix)
Does Mitochondrial Transport require a signal sequence?
Yes, found on the N-Terminus and composed of Arginine and Lysine amino acids
Is the signal sequence cleaved/ removed?
yes, it is cleaved when the chaperones fold the linear protein into its correct conformation and Signal Peptidase (enzyme) removes the signal sequence
Is the protein folded of linear when imported into the mitochondria
linear
