Lecture Set 11 Flashcards
How do proteins know where to go in the ER and Golgi?
ER
1) retention tags –> Arg-X-Arg = not going to Golgi
2) retrieval tags –> KDEL sequence
Golgi
1) retention tags
2) aggregation of proteins until it is too big to fit into vesicles
3) membrane thickness –> proteins will travel, membrane gets thicker until it perfectly matches size of hydrophobic core
How are proteins sent to lysosomes
mannose-6-phosphate tag binding to receptors in trans Golgi
phosphate removed to prevent rebinding to receptors (because they are recycled back to the Golgi)
what are 3 examples of a lysosomal storage disease?
inclusion cell disease –> M6P tag missing, can’t digest, proteins end up in PM
Pompe disease –> accumulation of glycogen
Tay-Sachs
How are vesicles sorted?
COPI –> used for retrograde transport from Golgi to ER, transport within Golgi
COP2 –> used for anterograde transport from ER to Golgi
clatherin –> targeting from TGN or P
What are the 3 different types of vesicles?
1) constitutive secretory –> immediate/constant release through exocytosis
2) regulatory secretory –> storage in vesicles until appropriate signal received
3) Lysosomal –> fuse with early endosomes
How does polarity affect sorting?
sends it to either basolateral or apical membrane, transcytosis can occur
Describe receptor-mediated endocytosis
ligand binds to receptor, migrates to clatherin-coated pit. clatherin is attached to adaptor proteins that determine the cargo, vesicle forms and is pinched off by dynamin. clatherins release, recycle to membrane, vesicle is now endosome
How do vesicles bind to the target?
Tethering factors stabilize orientation of vesicle, the V-SNARE interacts/binds with T-SNARE and allows Rab to facilitate fusion, SNAPS and NSF dissociates the SNAREs
What is the function of peroxisomes?
form hydrogen peroxides, oxidize molecules, helps for later degradation
