Signal transduction via small GTP-binding proteins - Ras as a Paradigm 2. Interaction with effectors

摘要

GTP-binding protein functions as molecular switches which cycle between the GTP-bound On-state and the GDP-bound OFF-state (Fig.l). They become activated by the action of guanine nucleotide exchange factors, GEF's, which increase the dissociation rate of nucleotide bound to the protein. The inactivation is achieved as a result of the intrinsically GTPase which is very slow and is catalyzed by GTPase-Activating Proteins, GAPs. In the GTP-bound state they interact with effectors or downstream targets which are defined as proteins interacting only, or rather much more strongly, with the GTP-bound active state [1.2].