Geranylgeranyltransferase type 1 or simply geranylgeranyltransferase is one of the three enzymes in the prenyltransferase group. In specific terms, Geranylgeranyltransferase (GGTase 1) adds a 20-carbon isoprenoid called a geranylgeranyl group to proteins bearing a CaaX motif: a four-amino acid sequence at the carboxyl terminal of a protein. Geranylgeranyltransferase inhibitors are being investigated as anti-cancer agents.[1]
Function
Prenyltransferases, including geranylgeranyltransferase, posttranslationally modify proteins by adding an isoprenoid lipid called a prenyl group to the carboxyl terminus of the target protein. This process, called prenylation, causes prenylated proteins to become membrane-associated due to the hydrophobic nature of the prenyl group. Most prenylated proteins are involved in cellular signaling, wherein membrane association is critical for function.[1]
Structure
Geranylgeranyltransferase contains two subunits, α and β that are encoded by the FNTA and PGGT1B genes, respectively. Both subunits are composed primarily of alpha helices. Geranylgeranyltransferase coordinates a zinc cation on its β subunit at the lip of the active site. Geranylgeranyltransferase has a hydrophobic binding pocket for geranylgeranyl diphosphate, the lipid donor molecule. All Geranylgeranyltransferase substrates invariably have a cysteine as their fourth-to-last residue. This cysteine, coordinated by the zinc, engages in an SN2 type attack on the geranylgeranyl diphosphate, displacing the diphosphate.[2][3]
^Reid TS, Terry KL, Casey PJ, Beese LS (October 2004). "Crystallographic analysis of CaaX prenyltransferases complexed with substrates defines rules of protein substrate selectivity". J. Mol. Biol. 343 (2): 417–33. doi:10.1016/j.jmb.2004.08.056. PMID15451670.
El Oualid F, Cohen LH, van der Marel GA, Overhand M (2006). "Inhibitors of protein: geranylgeranyl transferases". Curr. Med. Chem. 13 (20): 2385–427. doi:10.2174/092986706777935078. PMID16918362.