vesicles transport Flashcards
what determines the final location of proteins that end up in the prominent organelles in the cell? who is the exception to this?
proteins that end up in the mitochondria, peroxisomes, and nucleus do so by post translational means. they are made on free ribosomes and the transfer is mediated by the presence of organelle specific amino acid signal sequence. the exception are proteins destined for the ER they do not use this pathway
what are the steps of nuclear transport?
- cargo has nuclear recognition signal that is recognized by importin and binds to it.
- the complex then travel into the nucleous/ organelle.
- they are bound by Ran-GTP
- binding of Ran-GTP causes the cargo to dissoicate from the importing but Ran-GTP remains bound to importin.
- Ran-GTP bound to importin is tranported back out into the cytoplasm.
- they are bound by GAP which hydrolyzes GTP on Ran to GDP causes the Ran-importin complex to dissociate.
https: //www.youtube.com/watch?v=Q7F2vGwfsL8https://www.youtube.com/watch?v=Q7F2vGwfsL8
https: //www.youtube.com/watch?v=Q7F2vGwfsL8
which tranport pathway is mutated in Zellweger syndrom?
organelle localazation pathway of protein transport to the peroxisome.
what causes the actual disease in Zellweger syndrome?
ZS is not caused by a defective pathway but rather a mutation in the amino acid sequence. the recogntion sequence on the amino acid is mutated and thus cannot be recognized by importin and is never transported to the nucelus. the synthesized proteins with no ability to get in the peroxisome remain in the cytoplasm until they are degraded
contrary to popular belief, secretory protein synthesis begins in the
cytoplasm
unlike intracellular proteins, secretory proteins are transported
cotranslationally
when a secretory protein emerges from the cytoplasmic ribosome who is the first molecule to bind said protein and how does it do this?
when a secretory protein first emerges from the ribosome, it binds SRP (signal recognition peptide) which recognizes the signal peptide sequence on the N-terminus of the protein
what are the steps to cotranslational protein transport
remember the signal peptide is actually removed after the protein has been localized in theb ER lumen
why dont you ever find glycosilated proteins on the cytoplasm?
because glycosylation happens on the ER lumen
what is the path of a secretory protein?
ribosomes–>ER–>Golgi–> membrane
what is usually the sugar content of the glycosylation step?
cotranslational proteins are glycosylated with a 9 manos oligosachiride
what are the steps to COP-II vessicle assembly?
- inactive Sar-1 bound to GDP is phosphorylated by GEF to produce active Sar-1-GTP.
- Sar-1-GTP inserts into the ER membrane and exposes its binding site
- COP binds to Sar-1
- recruitment of other CCOP II subunits allows it to select which protein in the ER to find and transport.
where do the different protein coats transfer to?
COP II: ER-Golgi
COP I: retrograde (brings shit back to be reprocessed
Clatherine: cell surface to early endosome
TGN to late endosome
late endosome to TGN
even though each vesicle has its own Rab (Rab is on the cargo), what adds more specificity to vesicle transport
V-snares on the vesicle can onlyh bind to aparticular t-snare on the target/ membrane
what is a KDEL sequence?
process by which a miss routed protein is retrieved and brough back to the TGN for sorting
where does sorting of proteins to be tranfered to the lysosomes, cell membrane happen?
in the trans golgi netowork
if a protien is marked by the manose-6-phosphate residue where is it being transported?
lysosome
what are the steps to endocytosis?
- cargo binds to the receptors on the cell surface
- then clatherine binds to the lumen side of the receptors
- then the vesicle is formed and transported into the cell into the early endosome.
- in the early endosome, the vesicle is dissociated and the cargo broken down.
- from here the vesicles can either be returned to the cell surface or be sent to the lysosome to be degraded
why would there be a need to send the vesicles to be degraded?
it is a way of down regulation because the less vesicles yiu have on the surfface the less cargo would be transported into the cell
what causes hypercholestrolnemia?
defect in the coated pit binding site of the cell surface receptors
enveloped viruses (if you have the time)
a
