Figure 5: Reversible membrane association is usually achieved by the presence of different membrane targeting motifs. This is the case for isoprenylated and myristoylated proteins which require either another lipid (palmitoylation of N-Ras) or a polybasic stretch (K-Ras4B, MARCKS). Release from the membrane can be achieved by depalmitoylation (N-Ras), phosphorylation of residues near the polybasic stretch (K-Ras), or binding of ligands (MARCKS, Arf).