(S)-2,3-Di-O-geranylgeranylglyceryl Phosphate Synthase from the Thermoacidophilic Archaeon Sulfolobus solfataricus

Abstract

The core structure of membrane lipids of archaea have some unique properties that permit archaea to be distinguished from the others, i.e. bacteria and eukaryotes. (S)-2,3-Di-O-geranylgeranylglyceryl phosphate synthase, which catalyzes the transfer of a geranylgeranyl group from geranylgeranyl diphosphate to (S)-3-O-geranylgeranylglyceryl phosphate, is involved in the biosynthesis of archaeal membrane lipids. Enzymes of the UbiA prenyltransferase family are known to catalyze the transfer of a prenyl group to various acceptors with hydrophobic ring structures in the biosynthesis of respiratory quinones, hemes, chlorophylls, vitamin E, and shikonin. The thermoacidophilic archaeon Sulfolobus solfataricus was found to encode three homologues of UbiA prenyltransferase in its genome. One of the homologues encoded by SSO0583 was expressed in Escherichia coli, purified, and characterized. Radio-assay and mass spectrometry analysis data indicated that the enzyme specifically catalyzes the biosynthesis of (S)-2,3-di-O-geranylgeranylglyceryl phosphate. The fact that the orthologues of the enzyme are encoded in almost all archaeal genomes clearly indicates the importance of their functions. A phylogenetic tree constructed using the amino acid sequences of some typical members of the UbiA prenyltransferase family and their homologues from S. solfataricus suggests that the two other S. solfataricus homologues, excluding the (S)-2,3-di-Ogeranylgeranylglyceryl phosphate synthase, are involved in the production of respiratory quinone and heme, respectively. We propose here that archaeal prenyltransferases involved in membrane lipid biosynthesis might be prototypes of the protein family and that archaea might have played an important role in the molecular evolution of prenyltransferases.The structures of membrane lipids have some interesting and remarkable properties that enable us to distinguish archaea from other organisms, i.e. eukaryotes and bacteria (1) (Fig. 1). Although the archaeal "diether" membrane lipids are homologues of glycerolipids in other organisms, they differ with respect to the following features: 1) The hydrocarbon moieties of the archaeal lipids are fully reduced C 20 or C 25 prenyl groups, whereas the ordinary glycerolipids contain linear acyl groups. 2) The alkyl groups are attached to glycerol via an ether bond in archaeal lipids, while glycerol and the acyl chains are ester-bonded in the bacterial and eukaryotic glycerolipids.3) The two groups of membrane lipids have opposite chiralities at their glycerol moieties; in short, the glycerol moieties of the archaeal and other glycerolipids are sn-2,3-di-O-alkylated and sn-1,2-di-O-acylated, respectively. Moreover, the existence of circular "tetraether" lipids, which are synthesized from two molecules of diether lipids in methanogenic and thermophilic archaea, emphasizes the uniqueness of the archaeal membrane lipids.The biosynthesis of the core structure of archaeal membrane lipids has been studied to date (Fig. 2). The genes of (all-E) geranylgeranyl diphos...

The Crystal Structure of (S)-3-O-Geranylgeranylglyceryl Phosphate Synthase Reveals an Ancient Fold for an Ancient Enzyme

“…A back and forth swinging motion of ␣3* could also act like a molecular ratchet. In this way, the AfGGGPS TIM-barrel modification might promote the delivery of its hydrophobic product in proximity to the membrane bilayer, where the next enzyme in the pathway lies in wait (13).…”

“…At the same time, a magnesium counterion will support the pyrophosphate leaving group. Asp 13 , an absolutely conserved residue in all GGGPS proteins ( Fig. 2A), is well positioned to act as a ligand for a Mg 2ϩ ion.…”

“…Together, Asp 13 , Thr 39 , the surrounding backbone carbonyls and water molecules are excellent candidates to ligate the Mg 2ϩ -diphosphate group of GGPP. This scenario is supported by the fact that the amino acids around Asp 13 and Thr 39 are two of the most highly conserved regions within the GGGPS proteins ( Fig. 2A).…”

“…The enzyme catalyzing the first reaction, (S)-3-O-geranylgeranylglyceryl phosphate synthase (GGGPS), is a cytosolic protein that has previously been purified and enzymatically characterized from Methanobacterium thermoautotrophicum (9 -11) and Thermoplasma acidophilum (12). The enzyme catalyzing the second prenyltransfer, (S)-2,3-di-O-geranylgeranylglyceryl phosphate synthase, is an integral membrane protein which has recently been cloned and purified from Sulfolobus solfataricus (13). In ensuing reactions the isoprenoid double bonds are reduced and various polar headgroups may be attached to the lipid.…”

Identification of CDP-Archaeol Synthase, a Missing Link of Ether Lipid Biosynthesis in Archaea

“…The second ether bond is formed by the membrane protein DGGGP synthase that belongs to the UbiA prenyltransferase family. DGGGP synthase of Sulfolobus solfataricus was expressed in E. coli, and the enzymatic activity of the purified protein was found to be specific for the substrates GGPP and GGGP (Hemmi et al, 2004) synthesizing the product 2,3-di-O-geranylgeranylglyceryl phosphate (DGGGP). In a later study, DGGGP synthase was shown to accept both the S and R form of GGGP, thus being rather enantio unselective (Zhang et al, 2006).…”