Prenyl-protein transferases

Omer, C.A., Krai, A.M., Diehl, R.E., Prendergast, G.C., Powers, S., Allen, C.M., Gibbs, J.B., and Kohl, N.E. (1993). Characterization of recombinant human farnesyl-protein transferase cloning, expression, farnesyl diphosphate binding, and functional homology with yeast prenyl-protein transferases. Biochemistry 32 5167-5176. 

Prenyl-protein transferases consist of three members that include famesyl-protein transferase (FPTase) and two isoforms of geranylgerany 1-protein (GGPTase I and II) transferase. Farnesyl and geranylgerany 1 protein transferases catalyze the transfer of 15-carbon or 20-carbon isoprene units, respectively, to specific intracellular signaling proteins. The prenyl-protein transferase proteins are heterodimers consisting of a and P-subunits with approximate molecular weights of 48,000 and 45,000 Da, respectively [29]. 

Hasne, M.P., and Lawrence, F. (1999). Characterization of prenylated protein methyl-transferase in Leishmania. Biochem J 342(Pt 3) 513-518. 

In another application of coupling proteins to surfaces using click chemistry, Duckworth et al. (2006) carried out prenylation of a protein using a farnesyl azide derivative and the enzyme farnesyl transferase for subsequent chemoselective ligation to alkyne-functionalized agarose beads. The result is a highly discrete, site-specific attachment of the protein to the solid phase at a single location. 

Protein prenylation leads to an increased hydrophobicity of proteins, typically resulting in an increased affinity for membranes. In 2004 studies on the cellular location of prenylated RhoB proteins showed that RhoB can undergo farnesylation (RhoB-F) as well as geranylgeranylation (RhoB-GG). With the aid of specific prenyl transferase inhibitors, it was revealed that RhoB-GG is localized to multivesicular late endosomes. 

The following is a recent review on the molecular and physical properties of these transferases which prenylate suitable protein substrates. 

Keywords Farnesyl transferase inhibitor Protein prenylation Ras protein ... 

Rubber is synthesized by plants via a side branch of the isoprenoid pathway by the enzyme rubber transferase (dy-prenyl transferase systematic name poly-dy-polyprenyl-diphosphate isopentenyl-diphosphate polyprenylcistransferase EC 2.5.1.20). Surprisingly, although this process has been studied for decades, due to the labile nature of the rubber transferase and the fact that it is a membrane-associated enzyme present in relatively low abundance, the identification of its protein subunits remain elusive. For some recent reviews on rubber biosynthesis, please refer to [248-251]. 

Prenyltransferases are a class of enzymes that transfer allylic prenyl groups to acceptor molecules. Prenyl transferases commonly refer to prenyl diphosphate synthases (even though the class of prenyl transferases also includes enzymes that catalyze the transfer of prenyl groups to acceptors that include not only isopentenyl diphosphate (IPP) but also aromatic compounds and proteins etc.). 

The prenyl transferases are a class of enzymes that is involved in post-translational modification of membrane-associated proteins. These enzymes catalyze the transfer of a farnesyl (FTase, EC 2.5.1.58, for structural information see References 55-65) or geranyl-geranyl group (GGTase I, EC 2.5.1.59 GGTase n, EC 2.5.1.60, for structural information... 

Synthetic derivatives and analogs of prenyl diphosphates have historically played a key role in defining key featnres of the mechanism of enzymes that ntilize these key intermediates in the isoprenoid pathway. This has also been the case with the investigation of the protein prenyl-transferases. A brief introduction to the protein prenyltransferase enzymes is given along with outlines on the previous use of prenyl diphosphate tools and key aspects of their synthesis. The development of prenyl diphosphate-based FTase inhibitors is described. The use of prenyl diphosphate derivatives as mechanistic and structural probes is next discussed. In particular, the use of fluorinated, isotopically labeled, and photoaffinity derivatives is presented. An overview of the extensive work on the determination of FTase isoprenoid substrate specificity is then given, and the chapter concludes with a section on the development of prenyl diphosphate tools for proteomic studies. 

Turek, T.C., Gaon, L, Distefano, M.D., and Strickland, C.L. (2001). Synthesis of farnesyl diphosphate analogues containing ether-linked photoactive benzophenones and their application in studies of protein prenyltransferases. J Org Chem 66 3253-3264. Turek-Etienne, T.C., Strickland, C.L., and Distefano, M.D. (2003). Biochemical and structural studies with prenyl diphosphate analogues provide insights into isoprenoid recognition by protein farnesyl transferase. Biochemistry 42 3716-3724. 

Seabra, M.C., Goldstein, J.L., Sndhof, T.C., et al. (1992). Rab geranylgeranyl transferase A multisubunit enzyme that prenylates GTP-binding proteins terminating in Cys-X-Cys or Cys-Cys. J Biol Chem 267 14497-14503. 

Coxon, F.P., Ebetino, F.H., Mules, E.H., et al. (2005). Phosphonocarboxylate inhibitors of Rab geranylgeranyl transferase disrupt the prenylation and membrane localization of Rab proteins in osteoclasts in vitro and in vivo. Bone 37 349-358. 

GGTase-I [5], The specificities of FTase and GGTase are not absolute, and cross prenylation occurs which can be observed more readily for some substrates when one of the enzyme is inhibited. For example, K-Ras and N-Ras, which are the usual substrates for FTase, can be geranylgeranylated when the activity of FTase is suppressed [6]. The second and last steps of the modification process occur on the ER membrane and are catalyzed by Ras converting enzyme 1 (Reel) and isoprenylcysteine carboxylmethyl transferase (Icmt), both unique enzymes modify both farnesylated and geranylgeranylated proteins [1,7]. 

Kale TA, Hsieh SJ, Rose MW, Distefano MD. Use of synthetic isoprenoid analogues for understanding protein prenyl-transferase mechanism and structure. Curr. Top. Med. Chem. 2003 3 1043-1074. 

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