Midterm 2 Flashcards
Earl Sutherland performed a set of experiments we discussed in the class. He broke open liver cells, and separated soluble supernatant 1 from a membrane pellet. Then he resuspended the membrane, added EPI and spun again to get a supernatant 2. He found that supernatant 2 plus supernatant 1 efficiently stimulated the breakdown of glycogen. What essential signaling component was in Supernatant 1?
Glycogen Phosphorylase Kinase
What is true of a cell mutant for a t-SNARE that normally localizes on the cis-Golgi?
Secreted proteins would be stuck in an abundance of COPII vesicles
What would be the result of a double mutant defective for both sec12 (the Sar1 GEF) and the cis-Golgi t-SNARE?
The ER would be enlarged
Yeast and many other organisms make a single kind of clathrin coat. How is it then that a single clathrin coat can be used for three different transport pathways - Golgi to late endosomes, plasma membrane to early endosomes, and immature secretory vesicles to Golgi - that each involves different specialized cargo proteins?
Because each cargo protein binds to different adaptor proteins to provide specificity
You isolate a secretion defective mutant strain in yeast that has excess ER-to-Golgi transport vesicles. A mutation disrupting which of the following proteins could lead to such a phenotype?
Rab protein
Transmembrane protein was synthesized w/ N-terminus in the cytosol and C-terminus in the ER. Which of the following accurately depict the orientation of this protein as it travels through the endomembrane system?
- C-term in the trans-Golgi network
- N-term in the cytosol
Grb2 is reqired int he EGF receptor (EGFR) pathway. You have been given a mutant cell line that does not express Grb2. What new protein could you engineer and express to make the cell respond to EGF ligand?
Modify SOS to contain an SH2 domain
A familial hypercholesterolemia patient presents that is unable to internalize LDL from the blood. Tests determine that she makes LDL receptors, but they are mutant. The LDL receptors efficiently bind LDL on the plasma membrane, but are not observed in coated pits. Where is the mutation in this receptor?
The AP0=-2 binding domain
Cells communicate in ways that resemble human communication. Talking to people at a cocktail party is analogous to ___?
Paracrine signaling
In a genetic screen in yeast, sec genes were isolated which encode proteins essential for protein secretion. The sec4 gene encodes a Rab GTPase. A mutation in the sec4 gene causes the mutant Rab to remain in the GDP bound form. What would be the consequence in this mutant?
The mutant Sec4 protein could no longer bind to its effector
Brefeldin A (BFA) is a fungal metabolite which inhibits the exchange of GDP to GTP in a GTPase required for vesicular transport.When cells were treated w/ BFA, proteins that are normally localized to the Golgi appeared in the ER. Why?
Transport of COP-II coated vesicles from the ER to Golgi would be blocked
In class we watched a time-lapse video of a yeast cell that expressed the early Golgi enzyme Vrg4 fused to GFP and the late Golgi enzyme Sec7 fused to dsRed. The data in this video ruled out ___.
The vesicle transport model
The yeast URA3 is a cytosolic protein and it is essential for synthesis of Uracil. URA3 was modified to carry N-terminus import signal for the mitochondrial matrix. Cells carrying the modified URA3 were grown in the absence of Uracil. Most cells died, but some grew. Why did some cells grow in the absence of Uracil?
Because of mutation in Tim17
The topography of GPCR in the plasma membrane of the cell is w/ the N-term on the outside and the C-term in the inside. What would be the topology of this protein when synthesized in the ER?
Type IV-B membrane protein
What does mRNA + microsomes + GTP-gamma-S look like on an SDS-PAGE?
Lowest band
