Prenyltransferases and their substrates. Shown are the four classes of human prenyltransferases with α (PTAR1, FNTA (PTAR2), and RabGGTA (PTAR3)) and β (FNTB, PGGT1B, and RabGGTB) subunits and their substrates, recognition sequences, and accessory proteins. N/A, not applicable.