Materials traffic through the endomembrane system of eukaryotic cells via vesicl
ID: 78248 • Letter: M
Question
Materials traffic through the endomembrane system of eukaryotic cells via vesicles. There are two coat proteins COP I and COP II that assemble vesicles for transport along microtubules. COP I coated vesicles undergo retrograde transport, for example, to move materials from the Golgi back to the ER. COP II coated vesicles undergo anterograde transport to move materials from the ER outward.
(1 pt) Which motor protein (myosin, kinesin or dynein) interacts with COP I vesicles? ______________
(1 pt) Which motor protein interacts with COP II vesicles? ______________
(1 pt) Some proteins that traffic in this system contain a KDEL amino acid signal sequence for retention in the ER that interacts with a KDEL receptor protein. Would you expect the KDEL receptor protein to be found associated with COP I or COP II coated vesicles? _________
61.(4 pts total) There had been a long-standing controversy between two different hypotheses about the trafficking of proteins through the Golgi that was resolved in a set of experiments that you studied this semester.
A)(1pt) What were the two hypotheses?
B)(1pt) Briefly describe the critical experiments that solved this controversy making clear which hypothesis was confirmed.
C)(1pt) What experimental evidence would have confirmed the other hypothesis?
D) (1 pt) Given that the experiments you studied were done in unicellular yeast, which hypothesis would you favor for mammalian cells? (note: the genes involved in transport and modification are so strongly conserved between yeast and mammals that the mammalian genes work in yeast)
Explanation / Answer
Kinesin - Microinjecting into the cells with a presence of Kinesin protein for COPI dependent transport. This protein also involved in the COPI mediated golgi complex to endoplasmic reticulum transport.
Myosin – Non receptor proteins used for the transport with COPII. This protein binds to COPII and form budding vesicle.
KDEL are present only in the soluble ER proteins. The proteins present in the KDEL are usually bound to the KDEL receptor and COP I coated proteins. COPI coated proteins are fused with ER and return the ER resident proteins.