To test if viral proteins are transported between Golgi stacks in vesicles or are released into the cytosol by one Golgi stack and taken up by another, viral protein transport was examined between Golgi stacks of infected and uninfected cells. Which one of the following experimental designs would best distinguish these two hypotheses?

Correct option is C

Correct Answer
(c) 3
Explanation:
If viral proteins are transported in vesicles, they are protected from proteases by the vesicle membrane. If they are released into the cytosol, they would be exposed and degraded by proteases. Therefore, adding protease to the assay mix directly distinguishes between vesicle-mediated transport (protease-resistant) and cytosolic release (protease-sensitive).
Information Booster
· Vesicular transport protects cargo proteins by enclosing them within membrane-bound compartments.
· Protease protection assays test whether cargo is shielded from the cytosol, indicating vesicular transport.
· This method is independent of specific coat proteins and directly assesses cytosolic exposure.
Additional Knowledge
(a) Depleting clathrin affects Golgi-to-endosome or TGN trafficking, not intra-Golgi transport, so it does not directly test cytosolic release versus vesicular transport.
(b) COPII mediates ER-to-Golgi transport, not transport between Golgi stacks, making it irrelevant to this question.
(d) Detergent treatment disrupts membranes nonspecifically and would abolish both vesicular and non-vesicular transport, failing to distinguish between the two mechanisms.