ISSN 1068-1620, Russian Journal of Bioorganic Chemistry, 2010, Vol. 36, No. 3, pp. 396–399. © Pleiades Publishing, Ltd., 2010. Original Russian Text © A.N. Kondakova, E.V. Vinogradov, M.E. Shekht, A.A. Markina, B.Lindner@c, V. L. L’vov, P.G. Aparin, Yu.A. Knirel, 2010, published in Bioorgan- icheskaya Khimiya, 2010, Vol. 36, No. 3, pp. 429–432. 396 1 2 Bacteria Shigella, which are genetically closely related to E. coli, cause diarrhea and bacillary dysen- tery (shigellosis) [1]. Lipopolysaccharide (LPS, endotoxin) plays an important role in the recognition of pathogens by the host immune system and is one of the bacterial virulence factors [2–4]. The LPS consists of lipid A, an oligosaccharide core, and an O-polysac- charide (O-antigen) consisting of oligosaccharide O-units: from one (SR-form) to 20 or more (S-form). The structure of the O-antigen defines the immuno- specificity of bacteria and serves as the basis for sero- typing of bacterial strains [5]. The R-form LPS is devoid of any O-antigen. Lipid A is responsible for the ability of the LPS to activate the innate immunie sys- tem via the TLR4 receptor and, in case of an excessive production of proinflammatory cytokines, to cause endotoxic shock [6]. Modified LPSs and their compo- nents are promising candidates for new effective vac- cines, including those for prophylaxis of shigellosis. Determination of the LPS structure is necessary for a better understanding of its role in the pathogenesis of infectious diseases and for the consistency of the vac- cine formulation. 1 The article was translated by the authors. 2 e-mail: annakond@gmail.com. Abbreviations: C12:0, lauric acid; C14:0, myristic acid; 3HOC14:0, 3-hydroxymyristic acid; Hep, L-glycero-D-manno- heptose; Kdo, 3-deoxy-D-manno-oct-2-ulosonic acid; LPS, lipopolysaccharide; HSQC, heteronuclear single-quantum coherence spectroscopy; NOESY, nuclear Overhauser effect spectroscopy; TOCSY, total correlation spectroscopy. The O-antigens of S. flexneri types 1–5 are variants of one basic structure, which differ in the patterns of α-D-glucosylation and/or O-acetylation [7]. The LPS core of an R-mutant of S. flexneri type 4b [8] has a structure that is typical of E. coli R3 core [7–10]. There are indications that the same core structure is charac- teristic for the other S. flexneri types (except for type 6, which has the E. coli R1 core structure) (Refs. [11, 12] and authors’ unpublished data). However, recently a structure of the core of S. flexneri type 5 has been reported, which differs significantly from the R3 core structure [13]. In this work, we established the full core structure of S. flexneri type 5b and type 2a, which is the most prevalent clinical isolate from patients with shigellosis in Russia, and demonstrated that it corresponds to R3 core structure. In addition, we characterized lipid A of these bacteria, determined the structure of the O-unit, the position and the configuration of the linkage between the O-unit and the core in the SR-form LPS of S. flexneri type 2a. A low-molecular mass LPS was obtained from the culture fluids of S. flexneri types 2a (strain 1605) and 5b (strain 119) using ultrafiltration, enzymatic diges- tion (RNAse, DNAse, Proteinase K) and gel chroma- tography on Sephadex G-200 in the presence of deox- ycholate [14]. Negative ion electrospray ionization ion-cyclotron resonance Fourier transform mass spec- tra showed that it represents predominantly the R- form LPS, which consists of the core and lipid A and have the same composition in both types. The hetero- Structure of the Oligosaccharide Region (Core) of the Lipopolysaccharides of Shigella flexneri Types 2a and 5b 1 A. N. Kondakova a, c, 2 , E. V. Vinogradov a , M. E. Shekht b , A. A. Markina b , B. Lindner c , V. L. L’vov b , P. G. Aparin b , and Yu. A. Knirel a a Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, Moscow, 119991 Russia b Gritvak Enterprise, Moscow c Research Center Borstel, 23845 Borstel, Germany Received December 7, 2009; in final form, December 8, 2009 Abstract—The full structure of the lipopolysaccharide core of bacteria Shigella flexneri types 2a and 5b, the causative agents of bacillary dysentery (shigellosis), was established by chemical methods, high-resolution electrospray ionization mass spectrometry, and two-dimensional NMR spectroscopy. The structure of the O-antigen repeating unit and the configuration and position of the linkage between the O-antigen and the core were determined in the lipopolysaccharide of S. flexneri type 2a. Key words: Shigella flexneri, O-antigen, oligosaccharide, structure, lipopolysaccharide DOI: 10.1134/S1068162010030179 LETTER TO THE EDITOR