InterPro domain: IPR026873

This entry includes the beta subunit of geranylgeranyl transferase type-2 (GGTase-II), which is also known as Rab geranyl-geranyltransferase subunit beta, Bet2 and Ptb1. GGTase-II catalyses the transfer of a geranyl-geranyl moiety from geranyl-geranyl pyrophosphate to proteins having the C-terminal -XCC or -XCXC [ 1 , 2 , 3 ]. GGTase-IIs are a subgroup of protein prenyltransferases (PTases) of lipid-modifying enzymes. PTases catalyze the carboxyl-terminal lipidation of Ras, Rab, and several other cellular signal transduction proteins, facilitating membrane associations and specific protein-protein interactions. Prenyltransferases employ a Zn2+ ion to alkylate a thiol group catalyzing the formation of thioether linkages between cysteine residues at or near the C terminus of protein acceptors and the C1 atom of isoprenoid lipids (geranylgeranyl (20-carbon) in the case of GGTase-II). GGTase-II catalyzes alkylation of both cysteine residues in Rab proteins containing carboxy-terminal "CC", "CXCX" or "CXC" motifs. PTases are heterodimeric with both alpha and beta subunits required for catalytic activity. The beta subunit has an alpha 6 - alpha 6 barrel fold. In contrast to other prenyltransferases, GGTas-II requires an escort protein to bring the substrate protein to the catalytic heterodimer and to escort the geryanylgeranylated product to the membrane [ 4 , 5 ].

1. Phosphoisoprenoids modulate association of Rab geranylgeranyltransferase with REP-1. J. Biol. Chem. 276, 48637-43
2. Sequence of ptb1, a gene for the beta subunit of the type-II geranylgeranyltransferase from the fission yeast Schizosaccharomyces pombe. Yeast 12, 479-83
3. Bet2p and Mad2p are components of a prenyltransferase that adds geranylgeranyl onto Ypt1p and Sec4p. Nature 366, 84-6
4. Interaction of yeast Rab geranylgeranyl transferase with its protein and lipid substrates. Biochemistry 41, 6805-16
5. Yeast protein geranylgeranyltransferase type-I: steady-state kinetics and substrate binding. Biochemistry 36, 4552-7