a) What protein is critical for Golgi transport in a cell free system? How did B

Question

a) What protein is critical for Golgi transport in a cell free system? How did Block and colleagues discover it?

b)What are vesicle-coating proteins? Which ones are used for what steps of the secretory pathway

c)Describe what is meant by the term “dynamic instability” of microtubules and actin

. d)Describe or design experiments to show that a signal sequence is both necessary and sufficient for import of a protein into the ER

e)Describe the Jak/Stat pathway starting with either leptin or erythropoietin as the ligand.

Explanation / Answer

a) I didn't get what you want to in this question.

b) In simple words vesicle-coating proteins are the proteins which helps in traffiking and transport of vesicles from particular parent organelles to its particular destination organelles.

The vesicular transport consists:

The secretory pathway is a transport system that shuttles macromolecules (like lipids and proteins) between the different compartments via small vesicles in the cell. Several membrane-bound compartments like ER, Golgi, endosomes etc. are involved in secretory pathway and these organelles helps in traffiking and transport of proteins to their final detination.

c) After protein are synthesized in the cytosol they are meant to be secreted to different cell organelles via ER, Golgi, lysosomes, etc.From the cytosol these proteins are first imported into the ER lumen where N-linked oligosaccharides are added to it.These lumen proteins carry a special hydrophobic signal peptide which facilitates their transport by the recognition of signal recognition particle (SRP). These SRP, directs the growing polypeptide chain to a SRP receptor located on the cytosolic surface of the RER membrane.

If the hydrophobic amino acids from a signal sequence is deleted or mutated it won't be able to bind with signal recognition particle (SRP),and the protein will lost the ability to cross the ER membrane into the lumen.So it shows the importance of signal sequence in import of a protein into the ER lumen.

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