Group A, B, C, and G Streptococcus Lancefield antigen biosynthesis is initiated by a conserved α-d-GlcNAc-ß-1,4-l-rhamnosyltransferase.

Group A carbohydrate (GAC) is a bacterial peptidoglycan-anchored surface rhamnose polysaccharide (RhaPS) that is essential for growth of Streptococcus pyogenes and contributes to its ability to infect the human host. In this study, using molecular and synthetic biology approaches, biochemistry, radiolabeling techniques, and NMR and MS analyses, we examined the role of GacB, encoded in the S. pyogenes GAC gene cluster, in the GAC biosynthesis pathway. We demonstrate that GacB is the first characterized α-d-GlcNAc-ß-1,4-l-rhamnosyltransferase that synthesizes the committed step in the biosynthesis of the GAC virulence determinant. Importantly, the substitution of S. pyogenes gacB with the homologous gene from Streptococcus agalactiae (Group B Streptococcus), Streptococcus equi subsp. zooepidemicus (Group C Streptococcus), Streptococcus dysgalactiae subsp. equisimilis (Group G Streptococcus), or Streptococcus mutans complemented the GAC biosynthesis pathway. These results, combined with those from extensive in silico studies, reveal a common phylogenetic origin of the genes required for this priming step in >40 pathogenic species of the Streptococcus genus, including members from the Lancefield Groups B, C, D, E, G, and H. Importantly, this priming step appears to be unique to streptococcal ABC transporter-dependent RhaPS biosynthesis, whereas the Wzx/Wzy-dependent streptococcal capsular polysaccharide pathways instead require an α-d-Glc-ß-1,4-l-rhamnosyltransferase. The insights into the RhaPS priming step obtained here open the door to targeting the early steps of the group carbohydrate biosynthesis pathways in species of the Streptococcus genus of high clinical and veterinary importance.

Reversed-phase ion-pair high-performance liquid chromatography assay of polyprenyl diphosphate oligomer homologues.

A reversed-phase ion-pair high-performance liquid chromatography procedure was developed for the separation of polyprenyl diphosphate oligomer homologues obtained chemically from plant polyprenols. Tetrabutylammonium phosphate was used as the ion-pair reagent, and the dependence of the separation quality on pH of ion-pair reagent was investigated for the first time. The procedure is applicable for the control of commercial available polyprenyl monophosphates (the active components of veterinary drugs Phosprenyl and Gamapren) for the possible presence of polyprenyl diphosphate byproducts.

Plant polyisoprenoids and control of cholesterol level.

The ability of plant polyisoprenoids (polyprenols and polyprenyl phosphates) to diminish the levels of serum cholesterol affecting its biosynthetic pathway are highlighted here. Possible mechanism of such process is discussed. It is also noted that polyisoprenoids can prevent toxic injuries of the liver and restore disturbed hepatic functions. The possibility of polyprenyl phosphates to reveal at the same time anti-inflammatory action suppressing lipoxygenase activity and lowering the levels of proinflammatory cytokines will be illustrated. Attention will be focused on the potential usefulness of plant polyisoprenoids in the course of prevention and treatment of hypercholesterolemia. High efficiency for combined use of polyprenyl phosphate and ß-sitosterol, which leads to substantial enhancement of the ability to overcome hypercholesterolemia versus the individual constituents will be demonstrated.

Synthesis of a fluorescent acceptor substrate for glycosyltransferases involved in the assembly of O-antigens of enterohemorrhagic Escherichia coli O157 and O5.

The assembly of the repeating units of O-antigens in Gram negative bacteria is catalyzed by specific glycosyltransferases. Previously we used GlcNAc/GalNAcα-diphosphate-phenoxyundecyl as natural acceptor substrate analogs in assays of the transfer of radioactive sugars by bacterial glycosyltransferases. In order to develop new, fluorescence based assays we have synthesized a fluorescent acceptor P¹-[11-(anthracen-9-ylmethoxy)undecyl]-P²-(2-acetamido-2-deoxy-α-D-galactopyranosyl) diphosphate and have shown that the compound was an excellent acceptor for glucosyltransferase WbdN from Escherichia coli (E. coli) O157 and for galactosyltransferase WbwC from E. coli O5. This is the first report of the Gal-transferase activity of the wbwC gene product of E.coli O5. The presence of the fluorescent label in the acceptor molecule allows the detection of glycosyltransferase reaction products with high sensitivity, eliminating the need for radioactive nucleotide sugars.

Separation of polyprenyl phosphate oligomerhomologues by reversed-phase ion-pair high-performance liquid chromatography.

A simple and rapid method of reversed-phase ion-pair high-performance liquid chromatography (HPLC) with UV-detection on a common C(18) column in an isocratic mode with the addition of tetrabutylammonium phosphate for the separation of polyprenyl phosphate oligomerhomologues has been developed. The method was successfully applied to assay the composition of polyprenyl phosphates obtained from polyprenols isolated from mulberry (Morus alba) leaves and fir (Abies sibirica) needles (the active components of veterinary drugs Gamapren and Phosprenyl correspondingly).

Biochemical characterization of WbdN, a ß1,3-glucosyltransferase involved in O-antigen synthesis in enterohemorrhagic Escherichia coli O157.

The enterohemorrhagic O157 strain of Escherichia coli, which is one of the most well-known bacterial pathogens, has an O-antigen repeating unit structure with the sequence [-2-d-Rha4NAcα1-3-l-Fucα1-4-d-Glcß1-3-d-GalNAcα1-]. The O-antigen gene cluster of E. coli O157 contains the genes responsible for the assembly of this repeating unit and includes wbdN. In spite of cloning many O-antigen genes, biochemical characterization has been done on very few enzymes involved in O-antigen synthesis. In this work, we expressed the wbdN gene in E. coli BL21, and the His-tagged protein was purified. WbdN activity was characterized using the donor substrate UDP-[(14)C]Glc and the synthetic acceptor substrate GalNAcα-O-PO(3)-PO(3)-(CH(2))(11)-O-Ph. The enzyme product was isolated by high pressure liquid chromatography, and mass spectrometry showed that one Glc residue was transferred to the acceptor by WbdN. Nuclear magnetic resonance analysis of the product structure indicated that Glc was ß1-3 linked to GalNAc. WbdN contains a conserved DxD motif and requires divalent metal ions for full activity. WbdN activity has an optimal pH between 7 and 8 and is highly specific for UDP-Glc as the donor substrate. GalNAcα derivatives lacking the diphosphate group were inactive as substrates, and the enzyme did not transfer Glc to GlcNAcα-O-PO(3)-PO(3)-(CH(2))(11)-O-Ph. Our results illustrate that WbdN is a specific UDP-Glc:GalNAcα-diphosphate-lipid ß1,3-Glc-transferase. The enzyme is a target for the development of inhibitors to block O157-antigen synthesis.

11-Phenoxyundecyl phosphate as a 2-acetamido-2-deoxy-α-d-glucopyranosyl phosphate acceptor in O-antigen repeating unit assembly of Salmonella arizonae O:59.

A synthesis of 11-phenoxyundecyl phosphate and its biochemical transformation (using GlcNAc-P transferase from Salmonella arizonae O:59 membranes catalysing transfer of GlcNc-phosphate from UDP-GlcNAc on lipid-phosphate) into P(1)-11-phenoxyundecyl, P(2)-2-acetamido-2-deoxy-α-D-glucopyranosyl diphosphate are described.

Synthesis of a quaternary polyprenyl ammonium salt.

Reaction of primary C(55)-allylic alcohol moraprenol (WT(3)C(7-9)-OH, a polyprenol from mulberry leaves) with triethylamine in the presence of phosphorus oxychloride leads to a quaternary ammonium chloride with a good yield (72%) and high cis-stereoselectivity of the terminal isoprene unit. Cationic polyprenyl derivatives may be useful for transfection and immunological studies.

Chemical synthesis of dolichyl phosphates, their analogues and derivatives and application of these compounds in biochemical assays.

Several methods for simple and efficient chemical synthesis of dolichyl phosphates and their analogues and derivatives are briefly summarized with a special emphasis on chemical modification of phosphoryl group and preparation of dolichyl phosphates labelled at the omega-end and at the gamma-isoprene unit of the isoprene chain by fluorescent groups, 2-aminopyridine and 1-aminonaphtalene residues. Additionally, data on biochemical assays with application of the compounds mentioned above are presented.

Structural studies and mechanism of Saccharomyces cerevisiae dolichyl-phosphate-mannose synthase: insights into the initial step of synthesis of dolichyl-phosphate-linked oligosaccharide chains in membranes of endoplasmic reticulum.

Dolichyl-phosphate-mannose (Dol-P-Man) synthase catalyzes the reversible formation of a key intermediate that is involved as a mannosyl donor in at least three different pathways for the synthesis of glycoconjugates important for eukaryotic development and viability. The enzyme is found associated with membranes of the endoplasmic reticulum (ER), where it transfers mannose from the water soluble cytoplasmic donor, guanosine 5'-diphosphate (GDP)-Man, to the membrane-bound, extremely hydrophobic, and long-chain polyisoprenoid acceptor, dolichyl-phosphate (Dol-P). The enzyme from Saccharomyces cerevisiae has been utilized to investigate the structure and activity of the protein and interactions of the enzyme with Dol-P and synthetic Dol-P analogs containing fluorescent probes. These interactions have been explored utilizing fluorescence resonance energy transfer (FRET) to establish intramolecular distances within the protein molecule as well as intermolecular distances to determine the localization of the active site and the hydrophobic substrate on the enzyme's surface. A three-dimensional (3D) model of the enzyme was produced with bound substrates, Dol-P, GDP-Man, and divalent cations to delineate the binding sites for these substrates as well as the catalytic site. The FRET analysis was used to characterize the functional properties of the enzyme and to evaluate its modeled structure. The data allowed for proposing a molecular mechanism of catalysis as an inverting mechanism of mannosyl residue transfer.

Polyprenols as possible factors that determine an instructive role of the innate immunity in the acquired immune response.

Polyprenols are an integral part of all living cells including prokaryotic and eukaryotic ones. These compounds take part in biosynthesis of glycoproteins. We have found that phosphates of polyprenols may act as effective antiviral agents with a wide spectrum of activity. One of such antiviral agents received from Pinus sativum polyprenols was named phosprenyl. Earlier we showed that phosprenyl expressed direct antiviral effect, while having mild immunomodulatory activity. In the present study we further evaluated influence of phosprenyl on the immune system. The drug was found to inhibit an early phase of IL-1 and Con A interaction in spleen cells as well as lypoxigenase activity and expression of IL-2 receptors. At the same time, phosprenyl induced NK cell activity and early TNF-alpha production. Basing on all these data we proposed that polyprenols could be considered as a "label" which grants a possibility to the innate immune system to recognize infection at the early stages and govern the acquired immunity.

Role of Cytokines in Immunomodulatory Effects of Polyprenyl Phosphate: New Generation of Antiviral Drugs.

Immunomodulatory properties of sodium polyprenyl phosphate (PP) were studied in vivo and in vitro. After injection to mice, PP was shown to increase serum levels of TNF-alpha, IL-6, and IFN-gamma. The simultaneous inoculation of tick-born encephalitis virus (TBEV) and PP to mice resulted in earlier serum appearance of IL-6, TNF-alpha and IFN-gamma (at days 1, 2 and 3, respectively) compared with mice which have received PP only. In TBEV-infected mice (not injected with PP) cytokines in serum were registered later - at day 7 after infection. Development of the disease with subsequent death was observed in 100% of infected mice. In contrast, mortality of mice infected with TBEV and simultaneously treated with PP was decreased to 40%. The study of spleen cell proliferative activity in mice injected with PP revealed a modulating effect of the latter. In vitro PP decreased spleen cell and Con A-induced blast proliferation stimulated by Con A and rIL-2 respectively. This effect was dependent upon PP inhibition of IL-2 binding to IL-2 receptors. It was concluded that PP induced early cytokine production (IL-6, TNF-alpha) by cells of monocyte/macrophage origin and, apparently, provided protection of mice against viral infection. Thus, the main properties of PP are the following: absence of the expressed direct effect on cytokine production and co-stimulating effect in combination with a bystander stimulus (in this case - TBEV).