Catalyzes the transfer of a farnesyl moiety from farnesyl diphosphate to a cysteine at the fourth position from the C-terminus of several proteins having the C-terminal sequence Cys-aliphatic-aliphatic-X. The beta subunit is responsible for peptide-binding. (2E,6E)-farnesyl diphosphate + L-cysteinyl-[protein] = diphosphate + S-(2E,6E)-farnesyl-L-cysteinyl-[protein] Binds 1 zinc ion per subunit. Heterodimer of an alpha and a beta subunit (By similarity). Interacts with RAS1 and RAS2 (PubMed:31250536). Highly expressed in mycelium, conidium, conidial germination, early formed appressorium and the late infection hypha. Shows a significantly reduced endogenous cAMP level. Results in the reduction of hyphal growth and sporulation, and an increase in the sensitivity to various stresses. Attenuates virulence on the plant host by impairing appressorium-mediated penetration and invasive growth. Belongs to the protein prenyltransferase subunit beta family.