6. You have genetically engineered green fluorescent protein (GFP) containing a
ID: 275954 • Letter: 6
Question
6. You have genetically engineered green fluorescent protein (GFP) containing a KDEL sequence (GFP-KDEL). When GFP-KDEL is expressed in normal human fibroblasts and examined using fluorescence microscopy, the fluorescence appears diffuse across the cytoplasm. How would you explain this observations given that KDEL is supposed to be an ER-specific sorting sequence? A. This engineered GFP would not have a hydrophobic signal sequence to get it into the RER in the first place. B. The KDEL sequence would not be recognized because the protein is not in the right compartment. C. This engineered GFP would be synthesized on cytosolic ribosomes. Both A and B. A, B and C 7. In eukaryotes, ribosomes become associated with endoplasmic reticulum membranes when the messenger RNA passes through the translocon in the ER membrane a signal sequence on the ribosome interacts with the SRP receptor on the ER membrane. a signal sequence at the N-terminus of the protein being synthesized interacts with a signal recognition particle, which in turn binds to the SRP receptor on the ER membrane. a signal sequence on the mRNA interacts with the SRP receptor on the ER membrane. a signal sequence on the protein being synthesized interacts with the SRP receptor on the ribosome.Explanation / Answer
6. Most ER-resident proteins have KDEL sequence at their C-terminus. The KDEL sorting signal is recognized and bound by the KDEL receptor found on ER and cis-Golgi. The KDEL receptor acts mainly to retrieve proteins with the KDEL recognition sequence that have escaped to cis-Golgi network and return them to ER.
Therefore, the protein should be present in golgi network or vesicles that carry to and fro between ER and golgi.
A,B and C might be the answer.
7. SRP has two binding sites- one end of the SRP binds to a signal sequence on a growing polypeptide chain, while the other end binds to the ribosome itself. The SRP directs both the binding of the ribosome to the ER membrane and the insertion of the nascent polypeptide into the transmembrane channel.
Option C.
8. ER resident proteins have KDEL sequence, while transmembrane proteins of ER have KKXX signal.
Option D.
9. N-linked glycosylation occurs in RER.
Option D
10. Clathrin mediates the transport from Golgi complex to endosome as well as plasma membrane to endosome.
Option B.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.