Protein Targetting Flashcards
Where are proteins synthesised on free ribosome destined for
Cytosol, nucleus, peroxisomes and mitochondria
Where are protein synthesised on the RER destined for
Secretion, insertion into the membrane and lysosomes
What sequence do proteins destined to remain in the Er contain?
KDEL sequence
Where is the KDEL sequence found on proteins
C terminus
What proteins transport proteins with the KDEL sequence back to the ER
COP1 proteins
Where is the signal sequence for proteins destined to go to mitochondria found?
N terminus
What type of proteins bind to proteins destined to mitochondria
Heat shock proteins
What do heat shock proteins do?
Allow proteins to cross the mitochondrial membrane and pull the protein through the translocation machinery
What are the 2 translocation machine dies found the in the mitochondrial membranes
TOM (outer membrane) and TIM (inner membrane)
What happens to the protein once it enters the mitochondria
The protein folds and the signal sequence is cleaved
What is the signal sequence on proteins destined for lysosomes
Mannose-6-Phosphate
What do proteins destined for mitochondria contain to be recognised by enzymes that their mannose region needs phosphorylating
Signal patch
What happens to proteins once its bound to a M6P receptor
Transported in vesicles with a clathrate coat to lysosomes
What causes a dissociation between the receptor and protein
A pH change
What enzyme removes the phosphate group
Phophatase
What is I cell disease
Deficiency in the Kinase enzyme which phosphorylates the mannose group for proteins destined for lysosomes
What is the result of I cell disease
Bloated lysosomes as they don’t have enzymes to break down their contents
What is the sequence for proteins destined for the nucleus called
Nuclear translocation sequence
What binds to proteins destined for the nucleus
Importing
What is the role of Ran GTP in protein targeting for the nucleus
Binds to importin causing a conformational change which displaces the cargo protein
What is the signal sequence for proteins targeted for peroxisomes called
Peroxisomes targeting sequence
Where is the peroxisomes targeting sequence found
C terminus
What recognises the peroxisomes targeting sequence
PEX 5 receptors
How do proteins destined for peroxisomes enter
PEX proteins make up a complex in th emebrsne and form a pore
What is Zellweger syndrome
Syndrome resulting in mutations in PEX proteins.
What is cotranslational transport
When proteins move from ribosomes to the Golgi then out of the cell
What 2 types of secretion are there
Constitutive or regulated
Give an example of constitutive secretion
Collagen
Give an example of regulated secretion
Insulin
Where is the signal sequence found for proteins destined to be secreted
N-Terminus
Whatcsequence is present on proteins that get inserted into the membrane
Stop sequence
What shape will transmembrane domains of proteins have
Alpha helix
