Guanine nucleotide exchange factor

Guanine nucleotide exchange factor (or guanine exchange protein) (GEFs) is 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.

Examples of GEFs

• SOS - Son of Sevenless is a GEF that is important in the cell growth-regulatory MAPK/ERK pathway.

• eIF-2b - The eukaryotic initiation factor 2b regenerates eIF-2a for an additional cycle in protein synthesis initiation, i.e. its binding to the Met-t-RNA.

• Ras-GRF1

• G protein-coupled receptors function as GEFs for their cognate G proteins.

• Kalirin

See also

• nucleotide exchange factor
• guanine