This enzyme, along with protein geranylgeranyltransferase types I (EC
2.5.1.59) and II (EC
2.5.1.60), constitutes the protein prenyltransferase family of enzymes. Catalyses the formation of a thioether linkage between the C-1 of an isoprenyl group and a cysteine residue fourth from the C-terminus of the protein. These protein acceptors have the C-terminal sequence CA1A2X, where the terminal residue, X, is preferably serine, methionine, alanine or glutamine; leucine makes the protein a substrate for EC
2.5.1.59. The enzymes are relaxed in specificity for A1, but cannot act if A2 is aromatic. Substrates of the prenyltransferases include Ras, Rho, Rab, other Ras-related small GTP-binding proteins, gamma-subunits of heterotrimeric G-proteins, nuclear lamins, centromeric proteins and many proteins involved in visual signal transduction. A zinc metalloenzyme that requires Mg2+ for activity.
