Figure 3.

Regulation of Arf family small G proteins: (A) The state of the Arf small G proteins GTP binding and hydrolysis is regulated by Arf family guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), respectively. The membrane-associated GTP-Arf then recruits effectors such as cargo adaptor proteins, membrane lipid-modifying enzymes, and additional GEFs. (B) GDP-Arf associates with the surface of the membrane in a reversible manner. Exchange of GDP for GTP in Arf causes a conformational change of the switch (SW1 and SW2) and interswitch regions to enter the hydrophobic pocket occupied by the myristoylated N-terminal helix (red). GTP-Arf then associates tightly with the membrane via the exposed N-terminal helix.