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 where X is Ser, Ala, Met, Cys, or Gln. Required for the membrane localization of proteins such as a-factor, Ras proteins and other membrane proteins containing the C-terminal CAAX motif (PubMed:3533274, PubMed:2124698, PubMed:1860864, PubMed:1763050, PubMed:8424764, PubMed:8527442, PubMed:17142567). The beta subunit is responsible for isoprenoid and peptide-binding (PubMed:7878044, PubMed:8995312, PubMed:9380709, PubMed:9545274, PubMed:12667062). (2E,6E)-farnesyl diphosphate + L-cysteinyl-[protein] = diphosphate + S-(2E,6E)-farnesyl-L-cysteinyl-[protein] Binds 1 zinc ion per subunit. kcat is 4.5 sec(-1) with dansyl-GCVIA as substrate. Optimum pH is 7.8. Heterodimer of an alpha (RAM2) and a beta (RAM1) subunit. Decreases SKT5 farnesylation. Present with 3910 molecules/cell in log phase SD medium. Belongs to the protein prenyltransferase subunit beta family.