Intracellular Trafficking + Sorting of Proteins (Chapter 49) Flashcards
What is Signal Hypothesis?
Proteins synthesised on membrane bound ribosomes contain a signal sequence on their N-terminal.
What are Preproteins?
These are proteins which possess signal peptide that must be removed.
What cystolic proteins are formed?
- Mitochondrial
- Nuclear
- Perioxsomal
- Cystolic
What RER proteins are formed?
- GA Membrane
- Plasma Membrane
- ER Membrane
- Lysosomal enzymes
What is the exocytic pathway?
RER - > GA - > PM
What is “Constitutive pathway” and “Regulated Pathway”?
Constitutive is when we have constant formation of vesicles passing through the secretory pathway.
Regulated when the formation of vesicles can be turned off/on.
Roles of the GA?
- Processing of Oligosacharides
- Especially N-linked Glycoproteins
- also have enzymes involved in O-Glycolysation.
- Protein sorting as well (Trans part only involved in this)
1) What do Chaperones do?
2) What do they show?
3) Which region of protein do they bind to?
1) They stabilise unfolded or partially folded proteins.
2) Chaperones exhibit ATPase Activity.
3) Chaperones bind to Hydrophobic regions of Proteins - preventing their aggregation.
How do Chaperones work?
ADP-Chaperones have a high affinity to UNFOLDED Proteins.
They bind to it.
Then ADP is replaced for ATP, and with each cycle more folded protein is released.
1) What are Chaperonins?
2) What do Chaperonins do?
1) These are a second major class of Chaperones.
2) They form barrel like structures which separates the unfolded protein allowing them the environments for correct folding.
Give examples of Chaperonins in Bacteria and in Humans.
Bacteria - GroEL
Human - Hsp60
What is the uptake signal?
A signal found on cystolic proteins which targets them to their appropriate organelle.
Examples of Uptake Signals?
N-terminal Sequence --- ER KDEL/HDEL --- Membrane of ER Amino Leader --- Mitochondria NLS --- Nucleus PLS --- Perioxosome Mannose-6-phosphate --- Lysosome
What is Translocation?
The movement of a molecule through 2 membranes.
What do Proteins targeted to Mitochondria posses?
What’s the most common type of AA found in this sequence?
An Amino Leader sequence.
It has many:
-Hydrophobic AA and Positive AA.
What does TOM20/22 do?
Acts as a receptor on Mitochondria.
What is condition for protein to pass through the pore in Mitochondria?
What ensures this?
The pore is called TOM40.
To pass through it must be unfolded. This is ensured by chaperones such as Hsp70.
Which Protein which enters the mitochondrial matrix does not have a pre-sequence?
Cytochrome C.
Diameter of the Nuclear Pore?
9nm.
watch this be the multiple choice question that will make you pass… just wait.
Under which weight are molecules able to simply able to diffuse through the nuclear pore complex?
Below 40kDa.
What is involved in Nuclear Import?
- Ran
- GAP
- Importins
Explain the process of Nuclear Import.
1) Importin binds to cargo. This complex then associated with Ran-GDP. It enters the nucleus.
2) GEF converts GDP into GTP, which causes the release of the cargo.
3) Ran-GTP-Importin Complex leaves the NPC.
4) GAP then converts GTP into GDP allowing the release of Importin.
What are Karyopherins?
These are the family of proteins of the importins and exportins.