Module 2: Figure Arf signalling
Function of the Arf monomeric G-protein in signal transduction
When bound to GDP, Arf is inactive, but it is activated when the GDP is exchanged for GTP. This exchange is accelerated by guanine nucleotide-exchange factors (GEFs), but how these are activated is still somewhat of a mystery. In some cases, such as Golgi-specific brefeldin A resistant factor 1 (GBF1), activation depends on other G-proteins such as Rab1 (Module 4: Figure COPI-coated vesicles). The primary action of the Arfs is to stimulate actin polymerization and membrane remodelling during protein trafficking.