Comprehension - L12-L13 Flashcards
In lysosomes, the organelle is surround by what?
A double membrane structure known as the autophagosome
Soluble ER proteins usually contain the signal:
lys-asp-glu-leu (KDEL)
ER membrane proteins also have this retrieval signal:
lys-lys-X-X
What does Mannos 6-Phosphate do?
The residue acts as a sorting signal, directing proteins to the lysosome
What does the GGA adaptor do?
Connects clathrin to the MPRs
What is the MPR?
Transmembrane protein that recognizes and captures proteins with the mannose 6 phosphate signal
In the targeting of lysosomal enzymes to lysosomes, what does the G-protein Arf1-GTP do?
Binds to membrane and initiates formation of the budding vesicles and binding of the other coat proteins and induces membrane curvature when bound to GTP
What are the 3 domains in a GGA adaptor molecule?
Bind Arf1-GTP
Bind Clathrin
Bind to cytosolic tails of the MPR
What do sorting signals do?
Involved in directing proteins to the plasma membrane of polarized cells
In the endocytic pathway, what is bulk-phase endocytosis?
Pinocytosis
Non- specific uptake of extracellular fluids
In the endocytic pathway, what is receptor mediated endocytosis?
Clathrin mediated
Specific molecules bind to receptors on the extracellular surface
What does the AP2 complex do?
Links the cytoplasmic tails of plasma membrane receptors with clathrin
What is dynamin?
A G-protein required for the clathrin coated vesicle to bud from the membrane
- subunits form a ring
- GTP hydrolysis cause the vesicle to cleave and dynamin disassembles
What happens in the recycling pathway of endocytosis?
- Receptors mediate uptake of materials
- Receptors go to early endosome for sorting
- Ligands dissociate due to pH
- Receptors go to recycling component
- Vesicles return receptors to surface to be used again
What happens in the degradation pathway of endocytosis?
- Signal receptors bind ligands
- Goes to early endosome for sorting and matures into late endosome
- Late endosome fuses w lysosome for receptor degredation
