The Structure of the Core Region of the Lipopolysaccharide from Rhodocyclus gelatinosus Dr2

Efficient chemical synthesis of both anomers of ADP L-glycero- and D-glycero-D-manno-heptopyranose

A series of anomeric phosphates and ADP-activated L-glycero- and D-glycero-D-manno-heptopyranoses has been prepared in high overall yields, which provided model compounds and substrates in the elucidation of biosynthetic pathways and glycosyl transfer reactions of nucleotide-activated bacterial heptoses. The alpha-anomers of the heptosyl phosphates were obtained in high yield and selectivity using the phosphoramidite procedure, whereas the beta-phosphates were formed preferentially employing acylation of reducing heptoses with diphenyl phosphorochloridate. An efficient route to the formation of the nucleotide diphosphate sugars was elaborated by coupling of the O-acetylated phosphates with AMP-morpholidate followed by alkaline deprotection to furnish ADP-L- and D-glycero-alpha-D-manno-heptose in 84 and 89% yield, respectively. Deacetylation of the O-acetylated beta-configured ADP heptoses was conducted at strictly controlled conditions (-28 degrees C at pH 10.5) to suppress formation of cyclic heptose-1,2-phosphodiesters with concomitant release of AMP. Isolation of the unstable beta-configured ADP-heptoses by anion-exchange chromatography and gel-filtration afforded ADP L- and D-glycero-beta-D-manno-heptose in high yields.

Structure of the core oligosaccharide in the serotype O8 lipopolysaccharide from Klebsiella pneumoniae

Two classes of mutants with O-antigen-deficient lipopolysaccharides were isolated from the serotype O8 reference strain, belonging to Klebsiella pneumoniae subspecies ozaenae. These mutants were selected by resistance to bacteriophage KO1-2, which recognizes and lyses strains with lipopolysaccharide molecules containing the D-galactan II O antigen. Strain RFK-11 contains a defect in O-antigen synthesis and has a complete core, including the attachment site for O antigen. This mutation is complemented by a plasmid carrying the rfb (O-antigen biosynthesis) gene cluster from the related K. pneumoniae serotype O1. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the lipopolysaccharide from strain RFK-9 has a mobility typical of deep-rough lipopolysaccharide. RFK-9 lipopolysaccharide lacks the attachment site for O antigen. Lipopolysaccharides from strains RFK-9 and RFK-11 were isolated, and their structures were determined by methylation analyses, muclear magnetic resonance spectroscopy, and mass spectroscopy. The deduced O8 core oligosaccharide includes the partial core structure reported for the K. pneumoniae subspecies pneumoniae serotype O1 lipopolysaccharide (M. Süsskind, S. Müller-Leonnies, W. Nimmich, H. Brade, and O. Holst, Carbohydr. Res. 269:C1-7, 1995), consistent with the possibility of a conserved core structure within the species. The core oligosaccharide differs from those of the genera Salmonella and Escherichia by the absence of a hexose-containing outer core, the lack of phosphate residues in the inner core, and the presence of galacturonic acid residues.

Lipopolysaccharide of Rhodospirillum salinarum 40: structural studies on the core and lipid A region

The structural elucidation of lipid A of the cell wall lipopolysaccharide (LPS) of Rhodospirillum salinarum 40 by chemical methods and laser desorption mass spectrometry revealed the presence of a mixed lipid A composed of three different 1,4'bisphosphorylated beta (1 --> 6)-linked backbone hexosaminyl-hexosamine disaccharides, i.e. those composed of GlcN --> GlcN, 2,3-diamino-2,3-dideoxy-D-Glc-(DAG --> DAG, and DAG --> GlcN. Lipid A of R. salinarum contained preferentially 3-OH-18:0 and 3-OH-14:0 as amide-linked and cis delta 11-18:1 and c19:0 as ester-linked fatty acids. The mass spectra of the liberated acyl-oxyacyl residues proved the concomitant presence of 3-O-(cis delta 11-18:1)-18:0 and 3-O-(c19:0)-14:0 as the predominating diesters in this mixed lipid A. The glycosidically linked and the ester-linked phosphate groups of the backbone disaccharide were neither substituted by ethanolamine, phosphorylethanolamine, nor by 4-amino-4-deoxy-L-arabinose, in contrast to most of the enterobacterial lipid As. In the core oligosaccharide fraction, a HexA (1 --> 4)HexA(1 --> 5)Kdo-trisaccharide was identified by methylation analysis. The terminal HexA (hexuronic acid) is possibly 4-OMe-GalA, a component described here as an LPS constituent for the first time. LPS of R. salinarum showed a lethality in C57BL/10 ScSN (LPS-responder)-mice) of an order of 10(-1)-10(-2) of that reported for Salmonella abortus equi LPS, and it was also capable of inducing TNF alpha and IL6 in macrophages of C57BL/10ScSN mice.

The inner core region of Yersinia enterocolitica Ye75R (0:3) lipopolysaccharide

The inner-core region of the lipopolysaccharide of an UDPGalNAc-4-epimerase-deficient mutant of Yersinia enterocolitica 0:3, designated as Ye75R, was investigated using methylation analysis, 1D-13C-NMR and 2D-13C-NMR and 1H-NMR, as well as 31P-NMR, fast-atom-bombardment mass spectrometry (FAB MS) and FAB MS/MS in positive and negative modes. The isolated core heptasaccharide (OS) was composed of 2 units D-glucose, 3 units LD-heptose and 1 unit each of DD-heptose and 3-deoxy-D-manno-octulosonic acid. Methylation analysis indicated that OS was highly branched with terminal location of the two glucoses and the DD-heptose unit, which was partially (to about 40%) phosphorylated at C7. These combined studies allowed us to formulate the structure of the inner core region as shown in Scheme 1. The substitution of the 7-position of the terminally linked DD-heptose unit by phosphate could be recognized by MS characterization of permethylated DD-heptose-7-phosphate (alditol acetate) and the extent of the substitution by the ratio of the two well separated 1H signals of DD-heptose in 500-MHz 1H-NMR. Negative FAB MS of OS also indicated the presence of smaller amounts of two hexasaccharides, differing from OS in lacking either one terminal unit of D-glucose or of the terminal DD-heptose, and additionally of a pentasaccharide lacking two heptosyl units, namely the terminal DD-heptose and and the subterminal LD-heptose. The presence of the smaller oligosaccharides in the OS fraction was also recognized by the methylation analysis.

Influence of the supramolecular structure of free lipid A on its biological activity

The three-dimensional supramolecular structures and the states of order of the acyl chains of lipid A from different Gram-negative species were investigated at 40 degrees C, high water content (80-90%), and different [lipid A]/[Mg2+] molar ratios using synchrotron radiation X-ray diffraction and Fourier-transform infrared spectroscopy. Measurements were made on free lipid A from Salmonella minnesota R595, mono- and bi-phosphoryl, as well as those from the non-enterobacterial strains Rhodobacter capsulatus 37b4, Rhodopseudomonas viridis F, and Rhodocyclus gelatinosus 29/1. Parallel to differences in their chemical primary structure, the structural polymorphisms and states of order at 37 degrees C of the non-enterobacterial lipid A were found to be different from those of enterobacterial lipid A. A clear correlation between the supramolecular structure and previously determined biological activities was found. Lipid A with a strong preference for lamellar structures (Rb. capsulatus and Rp. viridis) are endotoxically inactive and lack cytokine-inducing capacity; the compounds assuming a mixed lamellar/nonlamellar structure (monophosphoryl lipid A from S. minnesota) are of lower toxicity in vivo, but may induce cytokines in vitro; those lipid A with a strong tendency to form non-lamellar inverted structures (lipid A from S. minnesota and Rc. gelatinosus) exhibit full endotoxicity in vitro and in vivo. In contrast, anti-complementary activity is most pronounced for compounds with lamellar and least expressed for those with inverted structures. The states of order at 37 degrees C vary non-systematically, exhibiting the highest values for lipid A of S. minnesota and the lowest for that of Rc. gelatinosus. We propose to extend the term 'endotoxic conformation', which is used to describe the conformation of a single lipid A molecule required for optimal triggering of biological effects, to 'endotoxic supramolecular conformation' which denotes the particular organization of lipid A aggregates in physiological fluids causing biological activity.