Catalyzes the transfer of a geranyl-geranyl moiety from geranyl-geranyl diphosphate to proteins having the C-terminal sequence Cys-Ile-Ile-Leu or Cys-Val-Leu-Leu. Acts, among other substrates, on Rho1 and Rho2 and CDC42 proteins. Participates in a RAS-like C-terminal modification of proteins involved in nuclear division and bud growth. It is involved in bud positioning and cell polarity (PubMed:2034682, PubMed:1400380). The beta subunit is responsible for isoprenoid and peptide-binding (PubMed:9109664, PubMed:10491163). geranylgeranyl diphosphate + L-cysteinyl-[protein] = diphosphate + S-geranylgeranyl-L-cysteinyl-[protein] Binds 1 zinc ion per subunit. kcat is 0.34 sec(-1) with dansyl-GCIIL as substrate (PubMed:9109664). kcat is 4.8 sec(-1) with GST-CAIL as substrate (PubMed:10491163). Optimum pH is 7.5. Heterodimer of an alpha (RAM2) and a beta (CDC43) subunit. Present with 3940 molecules/cell in log phase SD medium. Belongs to the protein prenyltransferase subunit beta family.