Question

In the previous figure, what would happen if you overproduce the SH₂ domain of GRB2 in a stimulated cell?

1) The receptor will not get phosphorylated
2) PTB would not bind to the receptor
3) Ras-GEF will bind to PIP3
4) GRB2 will bind to PTB
5) Scaffold protein will bind to the SH3 domain of GRB2
6) Ras will not be activated

Answer 1

Overproduction of the SH₂ domain of GRB2 in a stimulated cell would lead to several effects, including inactivation of Ras, disruption of PTB binding, and disruption of scaffold protein binding.

Step-by-step explanation:

If you overproduce the SH₂ domain of GRB2 in a stimulated cell, it would affect several downstream cellular events. Here are the effects:

1. Ras will not be activated: GRB2 is responsible for binding to the receptor and recruiting SOS, which activates Ras. If there is an excess of SH₂ domain, it will bind to the receptor and prevent the binding of SOS, resulting in the inactivation of Ras.
2. GRB2 will bind to PTB: The SH₂ domain of GRB2 normally binds to phosphorylated tyrosine residues on the receptor. If there is an excess of the SH₂ domain, it may bind to PTB (Phosphotyrosine binding domain), which can prevent the binding of PTB with the receptor.
3. Scaffold protein will bind to the SH3 domain of GRB2: The SH3 domain of GRB2 is responsible for binding to scaffold proteins, which help organize and coordinate signaling complexes. If there is an excess of the SH₂ domain, it may disrupt the binding of scaffold proteins, affecting signaling complex formation.