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.
Most prenylated proteins are involved in cellular signaling, wherein membrane association is critical for function.
[1] Geranylgeranyltransferase contains two subunits, α and β that are encoded by the FNTA and PGGT1B genes, respectively.
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.