Question

Looking ahead to Friday. How would comparing the FRET profiles for CFP-GRB2 and YFP-SOS before and following the addition of EGF to cells each expressing either HER1 or ErbB provide information about a specific function of the extracellular region of a normal RTK.

A. The extracellular region provides an SH2 binding site for GRB2

B. The extracellular region prevents RTK dimerization in the absence of its ligand.

C. The extracellular region provides an SH3 binding site for SOS.

D. The extracellular region is required for RTK dimerization in the absence of its ligand.

E. The sole function of the extracellular region is ligand binding.

Answer 1

CFP-Grb2 and YFP-SOS would give FRET OFF to FRET ON condition in an ideal cell after EGF addition. EGF can bind to HER1 or ErbB on the cell surface and that can induce the interaction between Grb2 and Sos resulting MAPK signaling activation.

From the given information, we cannot conclude any domain specificity or dimerization of RTKs. The only conclusion that can be drawan is

E. The sole function of the extracellular region is ligand binding.