Farnesyl

Protein isoprenylation is a post-translational modification that affects about 0.5% of cellular proteins and is essential for the biological activity of proteins. Two enzymes catalyze the attachment of two prenyl groups to the sulfhydryl group of carboxyl-terminal cysteine groups. Proteins which are prenylated by these enzymes have a distinct motif at the C-terminal of the protein, C-A1-A2-X (C = Cysteine, A1 & A2 = aliphatic amino acids). The two enzymes involved in this transfer are farnesyltransferase and geranylgeranyltransferase. These transfer a 15 carbon farnesyl or a 20 carbon geranygeranyl, respectively, from a prenyl-pyrophosphate to the protein. Examples of proteins containing this C-A-A-X motif are members of the Ras small G protein family, the nuclear lamins and the gamma subunit of trimeric G proteins. Prenylation of proteins is necessary for membrane association of proteins as well as protein-protein interactions and the nature of the linked isoprenyl group can influence the protein interactions, such as the interaction between G proteins and receptors.