Salmonella 0-polysaccharide specificity

The structures of polyprenyl diphosphate-linked intermediates of Salmonella O-specific-polysaccharide biosynthesis were confirmed by chemical synthesis of their analogs derived from the plant polyprenols ficaprenol and moraprenol (structurally related to bacterial polyprenol57) with the following study of their behavior as substrates of enzymic reactions. Synthetic polyprenyl a-D-galactopyranosyl diphosphate291,292 was found to serve as an effective acceptor for the transfer of L-rhamnosyl groups.293"295 Two synthetic, isomeric disaccharide derivatives,292 13 and296 14, were tested as acceptors for enzymic D-mannosyl transfer from GDP-Man, but only the former was found to be an efficient substrate.294... 

The factors that determine the degree of polymerization of the polysaccharides remain unclear. It seems that the process is not under strict control, as significant heterogeneity in chain length is observed for Salmonella O-specific polysaccharides.302 304 In some cases, the degree of polymerization was found to depend on the conditions of cultivation of the micro-... 

The block mechanism of chain assembly is characteristic for polymeric chains of the UGT type (see Salmonella O-specific polysaccharides 10-12 and 18) and the UG type (see capsular polysaccharides 25, 27, and 33), with UDP-activated sugars serving as initiators of chain growth. It seems rather safe to suggest that the biosynthesis of other polymers of these types occurs through a block mechanism as well. 

The chemical-enzymic approach to the synthesis of modified polysaccharides presents a good prospect for the preparation of small quantities of these polymers, which may prove very useful for immunochemical studies. The approach is certainly not limited by the specific case of Salmonella polysaccharides 10-12, and may well be extended to other polymers. The first results from this group322 show that several analogs of O-specific polysaccharides (18) of Salmonella serogroups C2 and C3 may be prepared through this approach. 

V. N. Shibaev, L. L. Danilov, T. N. Druzhinina, L. M. Gogilashvili, S. D. Maltsev, and N. K. Kochetkov, Enzymatic synthesis of Salmonella O-specific polysaccharide analogs from modified polyprenyl pyrophosphate sugar acceptors, FEBS Lett., 139 (1982) 177-180. 

V Shibaev Biosynthesis of salmonella O-antigenic polysaccharide specificity of glycosyl transferases... 

An anti-2-acetamido-2-deoxy-D-mannose immunoglobulin, MOPC 406, is an IgA that binds73 polysaccharides from Salmonella weslaco and Escherichia coli 031. These polysaccharides are known to contain 2-acetamido-2-deoxy-D-mannose,83 and it has been shown that the specificity of this protein is directed towards /3-D-linked 2-acetamido-2-deoxy-D-mannopyranosyl residues.84 Inhibition studies revealed that the apparent affinity of the methyl /3-D-glycoside for the combining region of MOPC 406 is high. 

As may be seen from Table I (see p. 327), MOPC 384 precipitates with the lipopolysaccharides from Proteus mirabilis sp2, Salmonella tranaroa, Escherichia coli 070, and Salmonella telaviv.7s Precipitation with the latter polysaccharide can be inhibited with methyl ct-D-galactopyranoside. No inhibition could be achieved by using p-aminophenyl 1-thio-a-D-galactopyranoside,85 but the specificity of this protein nevertheless appears to be for a-D-linked D-galac-topyranosyl residues. 

CDP-6-deoxy-D-xy/o-hexos-4-ulose (7b) serves as a precursor in the biosynthesis of CDP-3,6-dideoxyhexoses28,168 having the d-ribo (paratose, 3,6-dideoxy- D-glucose ), o-xylo (abequose, 3,6-dideoxy- D-galactose ), and d-arabino (tyvelose, 3,6-dideoxy- D-mannose ) configurations. These monosaccharides are characteristic components of O-specific polysaccharides from Salmonella and Yersinia pseudotuberculosis. 

Approximately 400 different glycosyltransferases are necessary in order to ensure the synthesis of those bacterial polysaccharides whose structures have thus far been elucidated. This estimate is based on the results of an analysis of the structures, made in order to ascertain how many different disaccharide fragments are present. An example of such an analysis is shown in Table V for the disaccharide sequences L-rhamnopyranosyl-D-galacto-pyranose, D-mannopyranosyl-L-rhamnopyranose, and D-galactopyranosyl-D-mannopyranose that are characteristic for the O-specific polysaccharides of Salmonella serogroups A, B, D, and E, the objects of many biosynthetic studies. Full details of similar analyses for other disaccharide sequences will be published elsewhere, as the resulting Tables are too voluminous for inclusion in this Chapter, but the most interesting results are summarized in Tables VI and VII. 

Incorporation of abequosyl side-chains in O-specific polysaccharides (12) of Salmonella serogroup B occurs at the stage of repeating-unit assembly. The polyprenyl trisaccharide diphosphate 16a serves as an acceptor for abequosyl transfer from its CDP derivative.83,307 A similar reaction was demonstrated with an enzyme preparation from Citrobacter.290 Polymerases from S. typhimurium83,308 and S. bredeney286 were able to act on the derivatives of linear trisaccharide 16a, but, in the former case, the efficiency of... 

Another example of O-specific polysaccharides that are assembled through the block mechanism are the polymers from Salmonella serogroups C2 and C3. Their polysaccharide chains (18) are composed97 of linear, tetrasaccharide repeating-units having abequosyl and D-glucosyl branches,... 

Preparation of modified, bacterial polysaccharides having monosaccharide analogs inserted into the polymeric chain is of interest for study of the structure-properties relationship in these biopolymers. Incorporation of chemically prepared, modified, biosynthetic precursors of the polymers in enzymic reactions seems a promising approach for achieving this aim. Such an approach, which may be termed chemical-enzymic synthesis, has now been studied by our group,439-441 using O-specific polysaccharides (10-12) of Salmonella serogroups B and E as an example. 

Figure 1 represents the general structure of Salmonella lipopolysaccharides. They contain an external polysaccharide, the O-antigenic chain, and an innermost component, termed lipid A. O-chain and lipid A are linked to each other by an oligosaccharide referred to as the core. O-Specific Chains. As indicated in Figure 1, O chains are in general made up of repeating units of di-, tri-, or higher oligosaccharides. In rare cases the O-chain is a homopolysaccharide. The structure of the O-chain is unique to each bacterial serotype great diversity is encountered in the structures of O-chains.

Figure 2. Specific immunoabsorbents for Salmonella O and R form antibodies. Key PS, O-specific polysaccharide, core, core fragment and GlcNHr glucosamine and fatty acids. Specific immunoabsorbents for lipid A antibodies have also been prepared (C. Galanos and D. Nerkar, unpublished results Luderitz et a ., 1982).

Synthesis of f -D-(l,6) linked disaccharides of N-fatty acylated 2-amino-2-deoxy-D-glucose an approach to the lipid A component of the bacterial lipopolysaccharide. Carbohydr. Res., 88, C10-C13 Kochetkov, N.K., Dmitriev, B.A., Malysheva, N.N., Chernyak, A.Ya., Klimov, E.M., Bayramova, N.E., and Torgov, V.I. (1975). Synthesis of O-p-D-mannopyranosy l-( 1 - 0-0-ot -L-rhamnopyranosy l-( 1 -3)-D-galacto-pyranose, the trisaccharide repeating-unit of the O-specific polysaccharide from Salmonella anatum. Carbohydr. Res. 15, 283-290... 

Synthesis of the tetrasaccharide repeating-unit of the O-specific polysaccharide from Salmonella senftenberg. Carbohydr. Res. 5 1, 269-27 1... 

The serogroup classification of Salmonella bacteria, according to the Kauffmann-White scheme (2), is based on the antigenic specificities which reside in the polysaccharide chain (the... 

Figure 3. Structures of the O-antigenic polysaccharide chain in Salmonella bacteria of serogroups C2 and C3 and a synthetic disaccharide glycoconjugate (O-antigen 8-specific). Results of immunofluorescence studies (IFL) of these structures.

Figure 4. Structures of the O-antigenic polysaccharide chains in Salmonella bacteria ofserogroup E and a synthetic trisaccharide gly coconjugate (O-antigen 3-specific). Results of ELISA and immunofluorescence (IFL) studies. Key m, S. anatum (03, 10) , S. senftenburg (01, 3, 19) , BSA a, S. typhimurium (04, 5,...

Cell-mediated Immune Reactions and Specificity for Salmonella 0-Polysaccharides... 

TABLE I. Salmonella typhimurium Infection in Calves Delayed Skin Reactivity with Specificity for O-Antigenic Polysaccharide Chain... 

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