Midterm 3- Pain Flashcards
Role of the Golgi
Sorts membrane lipids and processes incoming proteins via O glycosolation and pruning of carbohydrate side chains
Role of the two sides of the Golgi
Trans side- Associates with the plasma membrane and sorts and sends mature proteins for usage
Cis side- Sorts incoming proteins from the ER
Terminal glycosolation
Modification of the glycoprotiens through the removal or addition of sugars on the core oligliosaccharide within the lumen of the golgi
Importance of glycosolation process on proteins
1) Used in protein sorting
2)Helps create resistance against protease digestion
3)Used in cell cell recognition
4)Participation in regulation of immune cells
Two hypothesis for Golgi movement
1) Stationary cisternae model: Cisternae and enzymes stay in place while cargo moves in vesicles
2)Cisternal Maturation Model: Each layer of the cisternae matures from the cis towards the trans side of the Golgi carrying its cargo with it with the vesicles moving Golgi proteins between different maturation phases of the golgi
Anterograde
Movement of proteins forward in the golgi from cis to trans face, similar to exocytosis
Retrograde
Movement of protiens backwards in the golgi from trans to cis face, similar to endocytosis
Which studies support which Golgi theory
TEM- Cisternal maturation
Inhibition ER transport- Cisternal maturation
Florescence microscopy- Stationary Golgi
Two pathways for ensuring proper drop off of proteins to organelles
1)Retention tagging: when in the correct environment protein has low affinity for vesicles to transport it again
2)Retrieval tag: Tags that when read will lead to escaped protein being sent to proper location
Soluble ER specific protein tags
KDEL (Lys,Asp,Glu,Leu) is added to the C terminus of the protein and mediates return of proteins back to the ER
ER specific transmembrane protein tag
KKXX(Lys,Lys,any,any) found on their cytosolic domains that signal for a return back to the ER
KDEL retrieval process
1) Escaped KDEL molecules bind to KDEL receptors in the golgi
2)KDEL receptors begin aggregating escaped proteins and form a vesicle which will return them to the ER
3)At the ER the high Ph causes the KDEL receptors to dissociate from the proteins and returns to golgi
Lysosomes targeting tag
Phosphorylation of the mannose side chain creates the Mannose-6-phosphate tag which when read leads to proteins being delivered to lysosomes
Role of protein coats in vesicle transport
1)Curve the membrane to form the actual vesicle structure
2)select the components that will be carried in the vesicle
The layers of the vesicle and their function
1)Outer: Scaffolding for the vesicle
2)Inner: Contains adapters which bind to specific proteins and hold the outerlayer and the contents together
Three vesicle classes and their direction of transport
1)COPII- ER to endo ERGIC and golgi complex(Anterograde)
2)COPi- ERGIC and Golgi back to ER- retrograde
3)Clatherin Coated- plasma membrane to golgi
Send off of vesicle bud
1)Sar1 is turned from GDP to GTP causig SAR1 to insert its alpha helix into the membrane
2)After insertion SAR1 can recruit sec23 and 24 which form the inner membrane and begin the bending and V-snares embed inside
3)Sec 13 and 31 bind to form the vesicle outer later
4)Budding vesicle seperates from the ER
Receival of vesicle bud
1)Before ariving GTP is converted back into GDP on SAR1 allowing the sec proteins to dissociate
2) At destination contact of vesicle and target causes tethers proteins to pull them to port
3)RAB GDP becomes GTP recruiting the cytosolic tether proteins to allow docking
4)T-snare attaches to V-snare allowing the vesicle and target membrane to be pulled apart and fused
Dissociation of the V and T snares
NSF (N-ethylmalemide-sensitive factor) and SNAPs (soluble NSF attachment proteins) “pry apart” the SNAREs, using energy from ATP hydrolysis
Exocytosis
Vesicles content are release into an interior via fusion of a vesicle and membrane, exports
Endocytosis
Imports extracellular molecules via vesicle formation
3 types of exocytosis
1)Regulated secretion:Secretory vesicles accumulate until a chemical trigger for release
2)Polarize secretion: Secretion in one direction with localized binding
3)Constitutive secretion:unregulated continuous process of secretion
3 types of endocytosis
1)Bulk phase endocytosis: non specific movement of material into the cell
2)Receptor mediated endocytosis: Uses receptors to determine what to bring inside
3)Phagocytosis: Engulfing of large objects
Process of endocytosis
1)Specific moleules bind to a receptor on the outer leaflet
2)Lateral diffusion to clathern coated puts which concentrate receptors
3)Accumulation causes clathern buildup causing invagination to occur
4)Pit is pinched off via Dynamin ring