Isoprenoid Precursor Biosynthesis Research Articles

A picomolar inhibitor of the Plasmodium falciparum IPP pathway.

We identified MMV026468 as a picomolar inhibitor of blood-stage Plasmodium falciparum. Phenotyping assays, including isopentenyl diphosphate rescue of parasite growth inhibition, demonstrated that it targets MEP isoprenoid precursor biosynthesis. MMV026468-treated parasites showed an overall decrease in MEP pathway intermediates, which could result from inhibition of the first MEP enzyme DXS or steps prior to DXS such as regulation of the MEP pathway. Selection of MMV026468-resistant parasites lacking DXS mutations suggested that other targets are possible. The identification of MMV026468 could lead to a new class of antimalarial isoprenoid inhibitors.

Specific pathway abundances in the neonatal calf faecal microbiome are associated with susceptibility to Cryptosporidium parvum infection: a metagenomic analysis

BackgroundCryptosporidium parvum is the main cause of calf scour worldwide. With limited therapeutic options and research compared to other Apicomplexa, it is important to understand the parasites’ biology and interactions with the host and microbiome in order to develop novel strategies against this infection. The age-dependent nature of symptomatic cryptosporidiosis suggests a link to the undeveloped immune response, the immature intestinal epithelium, and its associated microbiota. This led us to hypothesise that specific features of the early life microbiome could predict calf susceptibility to C. parvum infection.ResultsIn this study, a single faecal swab sample was collected from each calf within the first week of life in a cohort of 346 animals. All 346 calves were subsequently monitored for clinical signs of cryptosporidiosis, and calves that developed diarrhoea were tested for Rotavirus, Coronavirus, E. coli F5 (K99) and C. parvum by lateral flow test (LFT). A retrospective case–control approach was taken whereby a subset of healthy calves (Control group; n = 33) and calves that went on to develop clinical signs of infectious diarrhoea and test positive for C. parvum infection via LFT (Cryptosporidium-positive group; n = 32) were selected from this cohort, five of which were excluded due to low DNA quality. A metagenomic analysis was conducted on the faecal microbiomes of the control group (n = 30) and the Cryptosporidium-positive group (n = 30) prior to infection, to determine features predictive of cryptosporidiosis. Taxonomic analysis showed no significant differences in alpha diversity, beta diversity, and taxa relative abundance between controls and Cryptosporidium-positive groups. Analysis of functional potential showed pathways related to isoprenoid precursor, haem and purine biosynthesis were significantly higher in abundance in calves that later tested positive for C. parvum (q ≤ 0.25). These pathways are either absent or streamlined in the C. parvum parasites. Though the de novo production of isoprenoid precursors, haem and purines are absent, C. parvum has been shown to encode enzymes that catalyse the downstream reactions of these pathway metabolites, indicating that C. parvum may scavenge those products from an external source.ConclusionsThe host has previously been put forward as the source of essential metabolites, but our study suggests that C. parvum may also be able to harness specific metabolic pathways of the microbiota in order to survive and replicate. This finding is important as components of these microbial pathways could be exploited as potential therapeutic targets for the prevention or mitigation of cryptosporidiosis in bovine neonates.

Characterization of the 1-Deoxy-D-xylulose 5-Phosphate synthase Genes in Toona ciliata Suggests Their Role in Insect Defense.

The first enzyme, 1-Deoxy-D-xylulose-5-phosphate synthase (DXS), in the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway for isoprenoid precursor biosynthesis has been reported to function differently according to species. However, the current state of knowledge about this gene family in Toona ciliata is limited. The TcDXS gene family was identified from the whole genome of T. ciliata by firstly using bioinformatics analysis. Then, the phylogenetic tree was built and the promoter cis-elements were predicted. Six DXS genes were identified and divided into three groups, which had similar domains and gene structure. They are located on five different chromosomes and encode products that do not vary much in size. An analysis of the cis-acting elements revealed that TcDXS genes possessed light, abiotic stress, and hormone responsive elements. Ultimately, TcDXS1/2/5 was cloned for an in-depth analysis of their subcellular localization and expression patterns. The subcellular localization results of TcDXS1/2/5 showed that they were located in the chloroplast envelope membranes. Based on tissue-specific analyses, TcDXS1/2/5 had the highest expression in mature leaves. Under Hypsipyla robusta stress, their different expressions indicated that these genes may have insect-resistance functions. This research provides a theoretical basis for further functional verification of TcDXSs in the future, and a new concept for breeding pest-resistant T. ciliata.

The Reductive Dehydroxylation Catalyzed by IspH, a Source of Inspiration for the Development of Novel Anti-Infectives.

The non-mevalonate or also called MEP pathway is an essential route for the biosynthesis of isoprenoid precursors in most bacteria and in microorganisms belonging to the Apicomplexa phylum, such as the parasite responsible for malaria. The absence of this pathway in mammalians makes it an interesting target for the discovery of novel anti-infectives. As last enzyme of this pathway, IspH is an oxygen sensitive [4Fe-4S] metalloenzyme that catalyzes 2H+/2e− reductions and a water elimination by involving non-conventional bioinorganic and bioorganometallic intermediates. After a detailed description of the discovery of the [4Fe-4S] cluster of IspH, this review focuses on the IspH mechanism discussing the results that have been obtained in the last decades using an approach combining chemistry, enzymology, crystallography, spectroscopies, and docking calculations. Considering the interesting druggability of this enzyme, a section about the inhibitors of IspH discovered up to now is reported as well. The presented results constitute a useful and rational help to inaugurate the design and development of new potential chemotherapeutics against pathogenic organisms.

'Candidatus Sarmatiella mevalonica' endosymbiont of the ciliate Paramecium provides insights on evolutionary plasticity among Rickettsiales.

Members of the bacterial order Rickettsiales are obligatorily associated with a wide range of eukaryotic hosts. Their evolutionary trajectories, in particular concerning the origin of shared or differential traits among distant sub-lineages, are still poorly understood. Here, we characterized a novel Rickettsiales bacterium associated with the ciliate Paramecium tredecaurelia and phylogenetically related to the Rickettsia genus. Its genome encodes significant lineage-specific features, chiefly the mevalonate pathway gene repertoire, involved in isoprenoid precursor biosynthesis. Not only this pathway has never been described in Rickettsiales, it also is very rare among bacteria, though typical in eukaryotes, thus likely representing a horizontally acquired trait. The presence of these genes could enable an efficient exploitation of host-derived intermediates for isoprenoid synthesis. Moreover, we hypothesize the reversed reactions could have replaced canonical pathways for producing acetyl-CoA, essential for phospholipid biosynthesis. Additionally, we detected phylogenetically unrelated mevalonate pathway genes in metagenome-derived Rickettsiales sequences, likely indicating evolutionary convergent effects of independent horizontal gene transfer events. Accordingly, convergence, involving both gene acquisitions and losses, is highlighted as a relevant evolutionary phenomenon in Rickettsiales, possibly favoured by plasticity and comparable lifestyles, representing a potentially hidden origin of other more nuanced similarities among sub-lineages.

Altering potato isoprenoid metabolism increases biomass and induces early flowering

Isoprenoids constitute the largest class of plant natural products and have diverse biological functions including in plant growth and development. In potato (Solanum tuberosum), the regulatory mechanism underlying the biosynthesis of isoprenoids through the mevalonate pathway is unclear. We assessed the role of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) homologs in potato development and in the metabolic regulation of isoprenoid biosynthesis by generating transgenic lines with down-regulated expression (RNAi-hmgr) or overexpression (OE) of one (StHMGR1 or StHMGR3) or two genes, HMGR and farnesyl diphosphate synthase (FPS; StHMGR1/StFPS1 or StHMGR3/StFPS1). Levels of sterols, steroidal glycoalkaloids (SGAs), and plastidial isoprenoids were elevated in the OE-HMGR1, OE-HMGR1/FPS1, and OE-HMGR3/FPS1 lines, and these plants exhibited early flowering, increased stem height, increased biomass, and increased total tuber weight. However, OE-HMGR3 lines showed dwarfism and had the highest sterol amounts, but without an increase in SGA levels, supporting a rate-limiting role for HMGR3 in the accumulation of sterols. Potato RNAi-hmgr lines showed inhibited growth and reduced cytosolic isoprenoid levels. We also determined the relative importance of transcriptional control at regulatory points of isoprenoid precursor biosynthesis by assessing gene-metabolite correlations. These findings provide novel insights into specific end-products of the sterol pathway and could be important for crop yield and bioenergy crops.

Overexpression of PtDXS Enhances Stress Resistance in Poplars.

1-Deoxy-d-xylulose-5-phosphate synthase (DXS) is the rate-limiting enzyme in the plastidial methylerythritol phosphate pathway (MEP). In this study, PtDXS (XM_024607716.1) was isolated from Populus trichocarpa. A bioinformatics analysis revealed that PtDXS had high homology with the DXSs of other plant species. PtDXS expression differed among plant tissues and was highest in young leaves and lowest in roots. The recombinant protein was produced in Escherichia coli BL21 (DE3), purified, and its activity evaluated. The purified protein was capable of catalyzing the formation of 1-deoxy-d-xylulose-5-phosphate (DXP) from glyceraldehyde-3-phosphate and pyruvate. A functional color assay in E. coli harboring pAC-BETA indicated that PtDXS encodes a functional protein involved in the biosynthesis of isoprenoid precursors. The treatment of P. trichocarpa seedlings with 200 μM abscisic acid (ABA), 200 mM NaCl, 10% polyethylene glycol6000, and 2 mM H2O2 resulted in increased expression of PtDXS. The ABA and gibberellic acid contents of the transgenic lines (Poplar Nanlin 895) were higher than wild types, suggesting that DXS is important in terpenoid biosynthesis. Overexpression of PtDXS enhanced resistance to S. populiperda infection. Furthermore, the transgenic lines showed decreased feeding by Micromelalopha troglodyta, supporting the notion that PtDXS is a key enzyme in terpenoid biosynthesis.

Induction of Terpene Biosynthesis in Berries of Microvine Transformed with VvDXS1 Alleles.

Terpenoids, especially monoterpenes, are major aroma-impact compounds in grape and wine. Previous studies highlighted a key regulatory role for grapevine 1-deoxy-D-xylulose 5-phosphate synthase 1 (VvDXS1), the first enzyme of the methylerythritol phosphate pathway for isoprenoid precursor biosynthesis. Here, the parallel analysis of VvDXS1 genotype and terpene concentration in a germplasm collection demonstrated that VvDXS1 sequence has a very high predictive value for the accumulation of monoterpenes and also has an influence on sesquiterpene levels. A metabolic engineering approach was applied by expressing distinct VvDXS1 alleles in the grapevine model system “microvine” and assessing the effects on downstream pathways at transcriptional and metabolic level in different organs and fruit developmental stages. The underlying goal was to investigate two potential perturbation mechanisms, the former based on a significant over-expression of the wild-type (neutral) VvDXS1 allele and the latter on the ex-novo expression of an enzyme with increased catalytic efficiency from the mutated (muscat) VvDXS1 allele. The integration of the two VvDXS1 alleles in distinct microvine lines was found to alter the expression of several terpenoid biosynthetic genes, as assayed through an ad hoc developed TaqMan array based on cDNA libraries of four aromatic cultivars. In particular, enhanced transcription of monoterpene, sesquiterpene and carotenoid pathway genes was observed. The accumulation of monoterpenes in ripe berries was higher in the transformed microvines compared to control plants. This effect is predominantly attributed to the improved activity of the VvDXS1 enzyme coded by the muscat allele, whereas the up-regulation of VvDXS1 plays a secondary role in the increase of monoterpenes.

Phage Display on the Anti-infective Target 1-Deoxy-d-xylulose-5-phosphate Synthase Leads to an Acceptor-Substrate Competitive Peptidic Inhibitor.

Enzymes of the 2‐C‐methyl‐d‐erythritol‐4‐phosphate pathway for the biosynthesis of isoprenoid precursors are validated drug targets. By performing phage display on 1‐deoxy‐d‐xylulose‐5‐phosphate synthase (DXS), which catalyzes the first step of this pathway, we discovered several peptide hits and recognized false‐positive hits. The enriched peptide binder P12 emerged as a substrate (d‐glyceraldehyde‐3‐phosphate)‐competitive inhibitor of Deinococcus radiodurans DXS. The results indicate possible overlap of the cofactor‐ and acceptor‐substrate‐binding pockets and provide inspiration for the design of inhibitors of DXS with a unique and novel mechanism of inhibition.

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

Senescence is a natural, energy-dependent, physiological, developmental and an ecological process that is controlled by the plant’s own genetic program, allowing maximum recovery of nutrients from older organs for the survival of the plant, as such; it is classified as essential component of the growth and development of plants. In some cases, under one or many environmental stresses, senescence is triggered in plants. Despite many studies in the area, less consideration has been given to plant secondary metabolites, especially the role of VTCs on plant senescence. This review seeks to capture the biosynthesis and signal transduction of VTCs, the physiology of VTCs in plant development and how that is linked to some phytohormones to induce senescence. Much progress has been made in the elucidation of metabolic pathways leading to the biosynthesis of VTCs. In addition to the classical cytosolic mevalonic acid (MVA) pathway from acetyl-CoA, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, originating from glyceraldehyde-3-phosphate (GAP) and pyruvate, leads to the biosynthesis of isoprenoid precursors, isopentenyl diphosphate and dimethyl allyl diphosphate. VTCs synthesis and emission are believed to be tightly regulated by photosynthetic carbon supply into MEP pathway. Thus, under abiotic stresses such as drought, high salinity, high and low temperature, and low CO2 that directly affect stomatal conductance and ultimately biochemical limitation to photosynthesis, there has been observed induction of VTC synthesis and emissions, reflecting the elicitation of MEP pathway. This reveals the possibility of important function(s) of VTCs in plant defense against stress by mobilizing resources from components of plants and therefore, senescence. Our current understanding of the relationship between environmental responses and senescence mostly comes from the study of senescence response to phytohormones such as abscisic acid, jasmonic acid, ethylene and salicylic acid, which are extensively involved in response to various abiotic and biotic stresses. These stresses affect synthesis and/or signaling pathways of phytohormones to eventually trigger expression of stress-responsive genes, which in turn appears to affect leaf senescence. Comparison of plant response to stresses in relation to patterns of VTCs and phytohormones biosynthesis indicates a considerable crosstalk between these metabolic processes and their signal to plant senescence.

A Single Arabidopsis Gene Encodes Two Differentially Targeted Geranylgeranyl Diphosphate Synthase Isoforms.

A wide diversity of isoprenoids is produced in different plant compartments. Most groups of isoprenoids synthesized in plastids, and some produced elsewhere in the plant cell derive from geranylgeranyl diphosphate (GGPP) synthesized by GGPP synthase (GGPPS) enzymes. In Arabidopsis (Arabidopsis thaliana), five genes appear to encode GGPPS isoforms localized in plastids (two), the endoplasmic reticulum (two), and mitochondria (one). However, the loss of function of the plastid-targeted GGPPS11 isoform (referred to as G11) is sufficient to cause lethality. Here, we show that the absence of a strong transcription initiation site in the G11 gene results in the production of transcripts of different lengths. The longer transcripts encode an isoform with a functional plastid import sequence that produces GGPP for the major groups of photosynthesis-related plastidial isoprenoids. However, shorter transcripts are also produced that lack the first translation initiation codon and rely on a second in-frame ATG codon to produce an enzymatically active isoform lacking this N-terminal domain. This short enzyme localizes in the cytosol and is essential for embryo development. Our results confirm that the production of differentially targeted enzyme isoforms from the same gene is a central mechanism to control the biosynthesis of isoprenoid precursors in different plant cell compartments.

Aryl Bis-Sulfonamide Inhibitors of IspF from Arabidopsis thaliana and Plasmodium falciparum.

2-Methylerythritol 2,4-cyclodiphosphate synthase (IspF) is an essential enzyme for the biosynthesis of isoprenoid precursors in plants and many human pathogens. The protein is an attractive target for the development of anti-infectives and herbicides. Using a photometric assay, a screen of 40 000 compounds on IspF from Arabidopsis thaliana afforded symmetrical aryl bis-sulfonamides that inhibit IspF from A. thaliana (AtIspF) and Plasmodium falciparum (PfIspF) with IC50 values in the micromolar range. The ortho-bis-sulfonamide structural motif is essential for inhibitory activity. The best derivatives obtained by parallel synthesis showed IC50 values of 1.4 μm against PfIspF and 240 nm against AtIspF. Substantial herbicidal activity was observed at a dose of 2 kg ha(-1) . Molecular modeling studies served as the basis for an in silico search targeted at the discovery of novel, non-symmetrical sulfonamide IspF inhibitors. The designed compounds were found to exhibit inhibitory activities in the double-digit micromolar IC50 range.

Comprehensive Assessment of Transcriptional Regulation Facilitates Metabolic Engineering of Isoprenoid Accumulation in Arabidopsis.

In plants, two spatially separated pathways provide the precursors for isoprenoid biosynthesis. We generated transgenic Arabidopsis (Arabidopsis thaliana) lines with modulated levels of expression of each individual gene involved in the cytosolic/peroxisomal mevalonate and plastidial methylerythritol phosphate pathways. By assessing the correlation of transgene expression levels with isoprenoid marker metabolites (gene-to-metabolite correlation), we determined the relative importance of transcriptional control at each individual step of isoprenoid precursor biosynthesis. The accumulation patterns of metabolic intermediates (metabolite-to-gene correlation) were then used to infer flux bottlenecks in the sterol pathway. The extent of metabolic cross talk, the exchange of isoprenoid intermediates between compartmentalized pathways, was assessed by a combination of gene-to-metabolite and metabolite-to-metabolite correlation analyses. This strategy allowed the selection of genes to be modulated by metabolic engineering, and we demonstrate that the overexpression of predictable combinations of genes can be used to significantly enhance flux toward specific end products of the sterol pathway. Transgenic plants accumulating increased amounts of sterols are characterized by significantly elevated biomass, which can be a desirable trait in crop and biofuel plants.

Isoprenoid precursor biosynthesis is the essential metabolic role of the apicoplast during gametocytogenesis in Plasmodium falciparum.

The malaria parasite harbors a relict plastid called the apicoplast and its discovery opened a new avenue for drug discovery and development due to its unusual, nonmammalian metabolism. The apicoplast is essential during the asexual intraerythrocytic and hepatic stages of the parasite, and there is strong evidence supporting its essential metabolic role during the mosquito stages of the parasite. Supply of the isoprenoid building blocks isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) is the essential metabolic function of the apicoplast during the asexual intraerythrocytic stages. However, the metabolic role of the apicoplast during gametocyte development, the malaria stages transmitted to the mosquito, remains unknown. In this study, we showed that production of IPP for isoprenoid biosynthesis is the essential metabolic function of the apicoplast during gametocytogenesis, by obtaining normal gametocytes lacking the apicoplast when supplemented with IPP. When IPP supplementation was removed early in gametocytogenesis, developmental defects were observed, supporting the essential role of isoprenoids for normal gametocytogenesis. Furthermore, mosquitoes infected with gametocytes lacking the apicoplast developed fewer and smaller oocysts that failed to produce sporozoites. This finding further supports the essential role of the apicoplast in establishing a successful infection in the mosquito vector. Our study supports isoprenoid biosynthesis as a valid drug target for development of malaria transmission-blocking inhibitors.

A chemical rescue screen identifies a Plasmodium falciparum apicoplast inhibitor targeting MEP isoprenoid precursor biosynthesis.

The apicoplast is an essential plastid organelle found in Plasmodium parasites which contains several clinically validated antimalarial-drug targets. A chemical rescue screen identified MMV-08138 from the "Malaria Box" library of growth-inhibitory antimalarial compounds as having specific activity against the apicoplast. MMV-08138 inhibition of blood-stage Plasmodium falciparum growth is stereospecific and potent, with the most active diastereomer demonstrating a 50% effective concentration (EC50) of 110 nM. Whole-genome sequencing of 3 drug-resistant parasite populations from two independent selections revealed E688Q and L244I mutations in P. falciparum IspD, an enzyme in the MEP (methyl-d-erythritol-4-phosphate) isoprenoid precursor biosynthesis pathway in the apicoplast. The active diastereomer of MMV-08138 directly inhibited PfIspD activity in vitro with a 50% inhibitory concentration (IC50) of 7.0 nM. MMV-08138 is the first PfIspD inhibitor to be identified and, together with heterologously expressed PfIspD, provides the foundation for further development of this promising antimalarial drug candidate lead. Furthermore, this report validates the use of the apicoplast chemical rescue screen coupled with target elucidation as a discovery tool to identify specific apicoplast-targeting compounds with new mechanisms of action.

Isoprenoid metabolism in apicomplexan parasites.

Apicomplexan parasites include some of the most prevalent and deadly human pathogens. Novel antiparasitic drugs are urgently needed. Synthesis and metabolism of isoprenoids may present multiple targets for therapeutic intervention. The apicoplast-localized methylerythritol phosphate (MEP) pathway for isoprenoid precursor biosynthesis is distinct from the mevalonate (MVA) pathway used by the mammalian host, and this pathway is apparently essential in most Apicomplexa. In this review, we discuss the current field of research on production and metabolic fates of isoprenoids in apicomplexan parasites, including the acquisition of host isoprenoid precursors and downstream products. We describe recent work identifying the first MEP pathway regulator in apicomplexan parasites, and introduce several promising areas for ongoing research into this well-validated antiparasitic target.

Influence of mevinolin on chloroplast terpenoids in Cannabis sativa.

Plants synthesize a myriad of isoprenoid products that are required both for essential constitutive processes and for adaptive responses to the environment. Two independent pathways for the biosynthesis of isoprenoid precursors coexist within the plant cell: the cytosolic mevalonic acid (MVA) pathway and the plastidial methylerythritol phosphate (MEP) pathway. In this study, we investigated the inhibitory effect of the MVA pathway on isoprenoid biosynthesized by the MEP pathway in Cannabis sativa by treatment with mevinolin. The amount of chlorophyll a, b, and total showed to be significantly enhanced in treated plants in comparison with control plants. Also, mevinolin induced the accumulation of carotenoids and α-tocopherol in treated plants. Mevinolin caused a significant decrease in tetrahydrocannabinol (THC) content. This result show that the inhibition of the MVA pathway stimulates MEP pathway but none for all metabolites.

Current development in isoprenoid precursor biosynthesis and regulation.

Isoprenoids are one of the largest classes of natural products and all of them are constructed from two precursors, isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). For decades, the mevalonic acid (MVA) pathway was proposed to be the only IPP and DMAPP biosynthetic pathway. This review summarizes the newly discovered IPP and DMAPP production pathways since late 1990s, their distribution among different kingdoms, and their roles in secondary metabolite production. These new IPP and DMAPP production pathways include the methylerythritol phosphate (MEP) pathway, a modified MVA pathway, and the 5-methylthioadenosine shunt pathway. Relative to the studies on the MVA pathway, information on the MEP pathway regulation is limited and the mechanistic details of several of its novel transformations remain to be addressed. Current status on both MEP pathway regulation and mechanistic issues is also presented.

Characterization of Arabidopsis FPS Isozymes and FPS Gene Expression Analysis Provide Insight into the Biosynthesis of Isoprenoid Precursors in Seeds

Arabidopsis thaliana contains two genes encoding farnesyl diphosphate (FPP) synthase (FPS), the prenyl diphoshate synthase that catalyzes the synthesis of FPP from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). In this study, we provide evidence that the two Arabidopsis short FPS isozymes FPS1S and FPS2 localize to the cytosol. Both enzymes were expressed in E. coli, purified and biochemically characterized. Despite FPS1S and FPS2 share more than 90% amino acid sequence identity, FPS2 was found to be more efficient as a catalyst, more sensitive to the inhibitory effect of NaCl, and more resistant to thermal inactivation than FPS1S. Homology modelling for FPS1S and FPS2 and analysis of the amino acid differences between the two enzymes revealed an increase in surface polarity and a greater capacity to form surface salt bridges of FPS2 compared to FPS1S. These factors most likely account for the enhanced thermostability of FPS2. Expression analysis of FPS::GUS genes in seeds showed that FPS1 and FPS2 display complementary patterns of expression particularly at late stages of seed development, which suggests that Arabidopsis seeds have two spatially segregated sources of FPP. Functional complementation studies of the Arabidopsis fps2 knockout mutant seed phenotypes demonstrated that under normal conditions FPS1S and FPS2 are functionally interchangeable. A putative role for FPS2 in maintaining seed germination capacity under adverse environmental conditions is discussed.

Structure of the GcpE (IspG)–MEcPP complex from Thermus thermophilus

Isoprenoid precursor biosynthesis occurs through the mevalonate or the methylerythritol phosphate (MEP) pathway, used i.e., by humans and by many human pathogens, respectively. In the MEP pathway, 2-C-methyl-d-erythritol-2,4-cyclo-diphosphate (MEcPP) is converted to (E)-1-hydroxy-2-methyl-but-2-enyl-4-diphosphate (HMBPP) by the iron–sulfur cluster enzyme HMBPP synthase (GcpE). The presented X-ray structure of the GcpE–MEcPP complex from Thermus thermophilus at 1.55Å resolution provides valuable information about the catalytic mechanism and for rational inhibitor design. MEcPP binding inside the TIM-barrel funnel induces a 60° rotation of the [4Fe–4S] cluster containing domain onto the TIM-barrel entrance. The apical iron of the [4Fe–4S] cluster ligates with the C3 oxygen atom of MEcPP.