Final answer:
Exposure of Rab proteins to GMP-CPP would result in their permanent activation, as GMP-CPP is a non-hydrolyzable analog of GTP. This can cause continuous vesicle trafficking and potentially mimic pathological conditions like cancer, where proteins are stuck in an active signaling state due to compromised GTPase activity.
Step-by-step explanation:
GMP-CPP is a non-hydrolyzable GTP analog often used in the study of G-protein mediated signal transduction. Rab proteins, which are a family of small GTPases, are involved in the regulation of vesicle trafficking. Normally, these proteins alternate between an active GTP-bound state and an inactive GDP-bound state. In their GTP-bound form, Rabs interact with effector proteins and promote vesicle movement and fusion.
When exposed to GMP-CPP, these Rab proteins would be locked in an active, GTP-like state because GMP-CPP cannot be hydrolyzed to GDP. This persistent activation would prevent the normal cycling between active and inactive states, potentially leading to continuous vesicle trafficking. This kind of perturbation could mimic gain-of-function mutations that are observed in some pathological conditions, such as cancer, where GTPase activity is compromised due to mutations, leading to the inability of the Ras G-protein to hydrolyze GTP into GDP.
In the context of Ras proteins and cancer, when the GTPase activity is inhibited, Ras remains in a permanently active state, continuously sending growth signals to the cell. This results in uncontrolled cell growth, which is a hallmark of cancer. Thus, exposing Rab proteins to GMP-CPP is expected to permanently activate them, causing potential disruption in the cell’s normal physiological processes.