Guanine nucleotide exchange factor

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Guanine nucleotide exchange factor (GEFs) are implicated in addressing system of vesicular transport. For example, Rab is GDP bound and inactive in the cytosol before contact with GEF. The membrane bound GEF catalyses the removal of GDP and GDI (GDP dissociation inhibitor) and their replacement with GTP. This allows the Rab protein to bind budding vesicles (e.g. clathrin coated vesicles). Un-coating of the vesicle allows an interaction between Rab and Rab effector (at the target site) which aids SNARE protein interactions.

"Son of sevenless" (SOS) is a GEF that is important in the cell growth-regulatory MAPK/ERK pathway.

Another well-known example for a GEFs is guanine nucleotice exchange factor eIF-2b (eukaryotic initiation factor 2b). It regenerates eIF-2a for an additional cycle in protein synthesis initiation, i.e. its binding to the Met-t-RNA.

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GTP-binding protein regulators

GTPase activating protein: Chimerin 1 - RasGAP - Neurofibromin 1

Guanosine nucleotide dissociation inhibitors

Guanine nucleotide exchange factor: EIF-2 - Son of Sevenless - Ras-GRF1

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