Most GTPases Are Present Inside the Cell at a Much

Multiple Choice

Most GTPases are present inside the cell at a much higher concentration than their upstream GAP and GEF proteins. Imagine a mutation in a certain GTPase, such as a Rab protein, resulting in an extremely tight binding between the GTPase and its GEF, and a very slow dissociation. What would you expect to happen in the cell as a result?

A) Rab proteins will be activated, because the tightly bound GEFs will be unavailable.
B) Rab proteins will be inactivated, because the tightly bound GEFs will be unavailable.
C) Rab proteins will be activated, because the Rab-GAPs will become activated.
D) Rab proteins will be inactivated, because their GAPs will become activated.
E) Rab proteins will be activated, because there are fewer GAPs available.