Bet2p and Mad2p are components of a prenyltransferase that adds geranylgeranyl onto Ypt1p and Sec4p.
Three different prenyltransferases have been identified in yeast and higher cells, the farnesyltransferase and the type I and type II geranylgeranyltransferases (GGTase). The farnesyltransferase and GGTase-I modify peptides in vitro with the CAAX (C, Cys; A, aliphatic residue; X, terminal amino acid) consensus motif. These enzymes are heterodimers that have different beta-subunits and a shared alpha-subunit. In yeast, the RAM2 gene encodes this alpha-subunit. RAM2 is also homologous to MAD2, a yeast gene whose product has been implicated in the feedback control of mitosis. We have shown that Bet2p is a component of the yeast GGTase-II (refs 6, 12) that geranylgeranylates Ypt1p, a small GTP-binding protein that mediates transport from the endoplasmic reticulum to the Golgi complex. Here we report that Mad2p is a component of this enzyme. Bet2p forms a complex with Mad2p that appears to bind geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate. The efficient transfer of geranylgeranyl onto small GTP-binding proteins requires the presence of an additional activity.
Jiang
Y
Y
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Rossi
G
G
Ferro-Novick
S
S
D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins / Q000378:metabolism* / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D064246:Mad2 Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D017368:Protein Prenylation / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity; D014166:Transferases / Q000378:metabolism*; D020691:rab GTP-Binding Proteins
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; C577695:MAD2 protein, S cerevisiae; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C489439:BET2 protein, S cerevisiae; C070117:Geranylgeranyltransferase Type II protein, S cerevisiae; D019204:GTP-Binding Proteins; C060755:YPT1 protein, S cerevisiae; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins