Protein prenyltransferase beta subunit - PFTB

Protein prenyltransferase (PTase) domain, beta subunit (alpha 6 - alpha 6 barrel fold). The protein prenyltransferase family of lipid-modifying enzymes includes protein farnesyltransferase (FTase) and geranylgeranyltransferase types I and II (GGTase-I and GGTase-II). They catalyze the carboxyl-terminal lipidation of Ras, Rab, and several other cellular signal transduction proteins, facilitating membrane associations and specific protein-protein interactions. Prenyltransferases employ a Zn2+ ion to alkylate a thiol group catalyzing the formation of thioether linkages between the C1 atom of farnesyl (15-carbon by FTase) or geranylgeranyl (20-carbon by GGTase-I, II) isoprenoid lipids and cysteine residues at or near the C-terminus of protein acceptors. FTase and GGTase-I prenylate the cysteine in the terminal sequence, CAAX; and GGTase-II prenylates both cysteines in the CC (or CXC) terminal sequence.