GTPases are active when bound to GTP and inactive when bound to GDP.[1][3] In the generalized receptor-transducer-effector signaling model of Martin Rodbell, signaling GTPases act as transducers to regulate the activity of effector proteins.[3] This inactive-active switch is due to conformational changes in the protein distinguishing these two forms, particularly of the “switch” regions that in the active state are able to make protein-protein contacts with partner proteins that alter the function of these effectors.[3]