1366 c. When EGF (ligand) binds to the EGFR B receptor) the receptor-ligand comp

Question

1366 c. When EGF (ligand) binds to the EGFR B receptor) the receptor-ligand complex is endocytosed. Researchers deleted amino acids from the Ct domain of the protein EGFRA1005-1017 1018 (panel B) and then screened for percent internalization in the presence of EGF (panel K). First, explain the difference in internalization between the normal and mutant forms of the protein. Next, why would the mutation affect internalization given your understanding of receptor mediated endocytosis. Rubric (4): results explained correctly (2). Correct explanation for why the mutation caused the result (2). 90.0 80.0 c 70.0 O 60.0 60.0 40.0 30.0 20.0 10.0 EGFREG EGFR o0s-1017 EGF d. To study endocytosis of the EGFR researchers used a dye to measure the acidification of EGFR containing vesicles. Sixty minutes after EGF treatment, EGFRs were found in a cellular compartment that had a lower pH (pH5) then the cytoplasm (pH7) Identify the cellular compartment . and explain how that compartment became acidic. Rubric (4: correct organelle (2). Why specific organelle became acidic (2). 0 5 10 15 20 25 30 35 Time (min)

Explanation / Answer

Answer c

In the process of internalization, the ligand after activation through receptors, moves inside the cell through vesicles. This occurs normally. If proteins are mutated, then the ligands will not move inside and then no endocytosis will occur.

In the mutation of Ct domain, the receptors will not have active sites for the ligand. This will cause no binding of ligands to the receptors and hence no activation will occur.

Answer d

In the endocytosis process, lysosomes digest foreign particles and form endosomes finally. The internal pH of lysosome is acidic because it contains lysozymes, which work in acidic pH.

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