Cell Bio Exam 3 Flashcards
What are the 2 main parts of the vesicular transport?
Vesicle budding and fusion
Default Pathway Route
Goes from RER to Golgi to plasma membrane (PM)
2 signals required to divert from the default pathway
- Retention signals
- diversion signals
Function of Golgi Apparatus
Plays critical role in biosynthesis, sorting, dispatching, and recycling of proteins to various parts of the cell
Structure of the Golgi apparatus
From entrance to exit:
1. cis golgi network
2. cis cisterna
3. medial cisterna
4. trans cisterna
5. trans golgi network
Function of the perinuclear (aka golgi apparatus)
To remove and add sugars to glycoproteins through the action of resident glycosidases and glycotransferases
What molecules in the golgi add on sugars
glycosyltransferases
What molecules in the golgi cleave sugars?
glycosidases
What 2 parts of the golgi apparatus make up the “sorting reticulum”
- cis golgi network
- trans-golgi network
Purpose of cis-golgi network
passes proteins to the cis-golgi stack or returns them to the ER
- basically sorts what comes into the golgi
Purpose of trans-golgi network
passes proteins to the plasma membrane, lysosomes, or secretory vesicles
- sorts where proteins go after exiting the golgi
purpose of the medial golgi
this is where the glycosidase and glycosyltransferase reactions occur
Purpose of the intra-golgi
Transport vesicles
What is the rate-limiting step in protein transport and secretion?
Export from the ER
Questions that ER machinery asks
Is the protein correctly folded and assembled with other subunits
If ER detects that proteins are not correctly folded what occurs?
The denatured or unfolded protein is degraded
What occurs if the ER detects that the protein is not correctly assembled with other subunits?
If protein is still attached to BiP or other chaperones, and is actively still undergoing folding, then proteins remains in the ER
What is BiP
BiP is a heat shock protein (part of HSP70 family) found in the ER that helps protein with folding
What occurs if the ER detects that the protein is correctly folded and assembled with other subunits?
The protein will be exported by the default pathway to the cis-Golgi network
What occurs to misfolded p in the ER lumen?
A misfolded p will be moved out back through the Sec61 complex where it will bind to a N-glycanase. This will lead to ubiquitin binding to it and the p will be degraded by a proteosome
2 ER Retention Signals
- BiP
- PDI
What is the sequence for ER retention signals?
KDEL, short AA sequence
What binds to KDEL sequence
KDEL receptors present in ER and cis-Gogli
KDEL Recycling Steps
- Secretory proteins and ER resident protein receptors are moved along the default pathway from the ER to the golgi. ER resident p are also sent to golgi in separate vesicles
- ER resident p containing KDEL sequence bind to the ER p receptors in the golgi and are then recycled back to ER
- return requires use of Microtubules