Thematic review series: Lipid Posttranslational Modifications. Structural biology of protein farnesyltransferase and geranylgeranyltransferase type I

Abstract

More than 100 proteins necessary for eukaryotic cell growth, differentiation, and morphology require posttranslational modification by the covalent attachment of an isoprenoid lipid (prenylation). Prenylated proteins include members of the Ras, Rab, and Rho families, lamins, CENPE and CENPF, and the g subunit of many small heterotrimeric G proteins. This modification is catalyzed by the protein prenyltransferases: protein farnesyltransferase (FTase), protein geranylgeranyltransferase type I (GGTase-I), and GGTase-II (or RabGGTase). In this review, we examine the structural biology of FTase and GGTase-I (the CaaX prenyltransferases) to establish a framework for understanding the molecular basis of substrate specificity and mechanism. These enzymes have been identified in a number of species, including mammals, fungi, plants, and protists. Prenyltransferase structures include complexes that represent the major steps along the reaction path, as well as a number of complexes with clinically relevant inhibitors. Such complexes may assist in the design of inhibitors that could lead to treatments for cancer, viral infection, and a number of deadly parasitic diseases.-Lane, K. T., and L. S. Beese. More than 100 proteins necessary for eukaryotic cell growth, differentiation, and morphology require posttranslational modification by the covalent attachment of an isoprenoid lipid (prenylation) (1). This modification is catalyzed by three protein prenyltransferases: protein farnesyltransferase (FTase) and protein geranylgeranyltransferase type I (GGTase-I), collectively termed the CaaX prenyltransferases, as well as protein GGTase-II (or RabGGTase) [reviewed in this series in (2)], whose substrates are limited to members of the Rab subfamily of G proteins. FTase and GGTase-I transfer a 15 or 20 carbon isoprenoid [donated by farnesyl diphosphate (FPP) or geranylgeranyl diphosphate (GGPP)], respectively, to the cysteine of a C-terminal CaaX motif, defined by a cysteine (C) residue, followed by two small, generally aliphatic (a) residues, and the X residue, which contributes significantly to specificity (Fig. 1) (3-9). Kinetic assays and analysis of lipidated CaaX proteins purified from the cell demonstrate the general preference of FTase for methionine, serine, glutamine, or alanine and the preference of GGTase-I for leucine or phenylalanine in the X position. Here, we review the structural biology of FTase and GGTase-I; the biochemical properties of these enzymes have been reviewed extensively elsewhere (1, 10-15).After covalent attachment of the isoprenoid in the cytoplasm, most CaaX proteins undergo two further prenylation-dependent processing steps at the endoplasmic reticulum (1): proteolytic removal of the aaX tripeptide by the CaaX protease Ras and a-factor-converting enzyme (Rce1), and carboxymethylation of the prenylcysteine residue by the enzyme Isoprenylcysteine carboxyl methyltransferase (Icmt). The fully processed proteins exhibit high affinity for cellular membranes and present a unique structure at thei...

Rab Proteins and the Compartmentalization of the Endosomal System

“…Rab GTPases are kept soluble in the cytosol and in the inactive (GDP-bound) conformation through association with Rab GDP-dissociation inhibitors (Rab-GDI) (Ullrich et al 1993;Gavriljuk et al 2013). Prenylation-addition of one or two geranyl-geranyl groups-on conserved carboxyterminal cysteine residues serves together with upstream hypervariable regions in promoting specific and stable membrane association (Sa-saki et al 1990;Chavrier et al 1991;Seabra et al 1991;Kinsella and Maltese 1992;Ullrich et al 1993;Seabra and Wasmeier 2004;Lane and Beese 2006;Wu et al 2010). Third, in the active, GTP-bound conformation, Rab GTPases bind effector proteins that "implement" their downstream effects.…”

Targeting the protein prenyltransferases efficiently reduces tumor development in mice with K-RAS-induced lung cancer

“…This process is called isoprenylation and is carried out by a pair of cytosolic enzymes, protein farnesyltransferase (FTase) and protein geranylgeranyltransferase type I (GGTase-I) (1). FTase and GGTase-I share a common α-subunit but have unique β-subunits that determine substrate specificity (2,3).…”

Phosphonocarboxylates Inhibit the Second Geranylgeranyl Addition by Rab Geranylgeranyl Transferase

“…Protein prenylation involves the formation of a thioether link between conserved C-terminal cysteines in protein substrates and farnesyl pyrophosphate (FPP) 7 or geranylgeranyl pyrophosphate (GGPP) (2,3). These prenyl pyrophosphates, which originate from the mevalonate pathway are utilized by three different prenyltransferase enzymes (2,3). Farnesyl transferase (FT) and geranylgeranyl transferase type I (GGT-I) transfer FPP or GGPP, respectively, to a cysteine residue in the context of a C-terminal CAAX motif, where C is a cysteine, A is an aliphatic residue, and X is any amino acid.…”