Correct option is A
Explanation-
A. Treat one set of microsomes first with detergent and then with protease - Essential control
This treatment permeabilizes membranes with detergent (solubilizing the ER membrane), so all proteins, whether membrane-bound, lumenal, or cytosolic, become accessible to protease. It is used as a positive control to show total protein digestion (to validate protease activity).
B. Treat one set of microsomes with protease only - Essential control
It is used to tests whether proteins are exposed on the cytosolic side of the microsome membrane. Proteins protected from protease are likely inside the microsome (i.e., lumenal), while degraded ones are on the cytosolic surface.
C. Treat one set of microsomes with micrococcal nuclease.
This degrades nucleic acids, not proteins. It is used for experiments dealing with RNA protection or mRNA localization, but not directly relevant to testing ER protein transport or topology in this context.
Hence , not relevant for protein transport experiment
D. Treat one set of microsomes with detergent only - Essential control
It disrupts membranes without protease. It is useful to confirm that detergent itself doesn't degrade proteins and helps solubilize them.
Correct Option: a - A, B, and D only
These represent the best combination of controls for analyzing protein localization and protection in the ER/microsomal system:
A: Total accessibility (positive control)
B: Surface accessibility (cytosolic exposure)
D: Membrane disruption control
