c-erb-B2 is a mutant protein that is structurally related to the Epidermal Growt

Question

c-erb-B2 is a mutant protein that is structurally related to the Epidermal Growth Factor (EGF) receptor. Over expression of this protein can lead to transformation of cells, and large amounts of this protein are often found in metastatic breast tumor cells. Surprisingly, addition of EGF to cells expressing c-erb-B2 does not dramatically increase their growth rate, and addition of antibodies that block EGF binding to its receptor do not inhibit growth. Inhibitors of protein tyrosine kinases severely reduce growth of these cells. Which of the following best characterizes the nature of the mutation in cerb-B2? o a. The intracellular domain is missing and is ligand dependent b. The mutant receptor is trapped in the endoplasmic reticulum. The transmembrane domain is changed so that the receptor can no longer dimerize but is still ligand dependent d. The transmembrane domain is changed so that the receptor is always dimerized, but is stil ligand dependen e. The extracellular domain is missing, and the intracellular domain is constitutively phosphorylated, active and ligand independent

Explanation / Answer

Answer : (d) the transmembrane domain is changed so that the receptor is alwaysdimerised, but is still Logan's dependent.

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