Correct option is B
Explanation of the correct answer:
Interpretation A: "Protein X is a peripheral membrane protein" is likely correct because the fact that protein X can be extracted from the plasma membrane using high salt concentrations suggests that it is a peripheral membrane protein. Peripheral membrane proteins are not embedded in the membrane but are loosely associated with the membrane, often by ionic interactions. These proteins can be dissociated from the membrane using salt without disrupting the membrane itself.
Interpretation D: "Protein X is on the cytosolic face of the plasma membrane" is also likely correct. The treatment with protease of intact erythrocytes (cells are intact) followed by extraction resulted in intact protein X, suggesting that the protein is on the cytosolic face where protease can access it, without disrupting the cell membrane. The fact that fragmented protein X was obtained from disrupted membranes suggests that the protein could be accessible on the cytosolic face, which supports its localization.
Why other options are incorrect:
Option 1 (A and C):Interpretation C suggests that protein X is on the extracellular matrix face of the plasma membrane. However, the experimental data (protease treatment and intact protein extraction) suggest that protein X is more likely on the cytosolic face rather than the extracellular matrix face. So, A and Cis not correct.
Option 3 (B and C):Interpretation B suggests that protein X is an integral membrane protein, which would be embedded in the membrane, requiring stronger detergents or other harsher methods to remove. However, the use of high salt concentrations for extraction suggests protein X is a peripheral membrane protein, not an integral membrane protein. Thus, B and Cis incorrect.
Option 4 (B and D):Interpretation B suggests that protein X is an integral membrane protein, which contradicts the results from the high salt concentration treatment (indicating peripheral protein). Therefore ,B and Dis incorrect.
