What is a characteristic feature of small GTPases like Ras proteins?

Small GTPases, such as Ras proteins, act as molecular switches that are activated when bound to GTP (guanosine triphosphate) and deactivated when hydrolyzed to GDP (guanosine diphosphate). The characteristic feature of these proteins is their ability to undergo conformational changes upon GTP hydrolysis. When GTP is hydrolyzed to GDP, Ras undergoes a significant structural change that affects its interactions with downstream effector proteins. This switch-like mechanism allows Ras to control various signaling pathways, influencing processes such as cell growth, differentiation, and survival.

The ability to change shape upon GTP hydrolysis is fundamental to the function of Ras in signaling cascades, making it a critical mechanism in cellular regulation and communication. This conformational change is what allows the protein to toggle between an active and inactive state in response to different signaling stimuli.