Structural elucidation of the outer core tetrasaccharide isolated from the LPS of Rhizobium leguminosarum bv. trifolii strain 24. (29th May 2015)

• Record Type: Journal Article
• Authors: Turska-Szewczuk, Anna; Russa, Ryszard; Karaś, Magdalena A.; Danikiewicz, Witold; Spólnik, Grzegorz
• Is Part Of: Carbohydrate research. Volume 409(2015)
• Page Start: 1
• Page End: 8
• Publication Date: 2015-05-29
• Subjects: Rhizobium leguminosarum -- Outer core oligosaccharide -- Lipopolysaccharide -- Kdo -- QuiNAc -- Rha; Carbohydrates -- Periodicals; Chemistry, Organic -- Periodicals; Biochemistry -- Periodicals; Carbohydrates -- Periodicals; Chimie organique -- Périodiques; Glucides -- Périodiques; Biochemistry; Carbohydrates; Chemistry, Organic; Periodicals; Electronic journals; 507.78
• DOI: 10.1016/j.carres.2015.03.011
• Languages: English
• ISSNs: 0008-6215

Abstract

Abstract: The outer core oligosaccharide (OS) was isolated from the lipopolysaccharide (LPS) of Rhizobium leguminosarum bv. trifolii strain 24 after Smith degradation and then studied by sugar and methylation analyses along with NMR and mass spectrometry methods. Negative-ion electrospray (ESI-MS) mass spectrum showed two molecular ions at m / z 686.3 and 728.3, which corresponded to the core OS having the composition Rha2 QuiNAcKdh. The mass difference between both ions indicated that the higher molecule mass represented the mono O-acetylated variant of the OS. The sequence of the oligosaccharide was reflected in CID MS/MS spectra. In turn, NMR spectroscopy confirmed the composition and glycosylation pattern of the core OS and provided additional evidence on its structure. 2D NMR experiments revealed that the terminal Rha p is acetylated at position O-2. Moreover, 3-deoxyheptulosonic acid (Kdh), which was detected at the reducing terminus of the OS, was evidently derived from the Kdo as a result of Smith degradation. In addition, the higher intensity of signals for a six-membered pyranose ring of Kdh p over 2, 7- anh -Kdh f seemed to indicate prevalence of this form of the sugar in the OS-derived species. Based on the data obtained, the following structure of the outer core tetrasaccharide, which probably links the O-chain polysaccharide to the inner core in the LPS of R. leguminosarum bv. trifolii strain 24, was established: Graphical abstract: Highlights: Structure of the outer core of Rhizobium leguminosarum bv. trifolii 24 LPS was elucidated. The core has a tetrasaccharidic structure and the Rha2 O AcQuiNAcKdo composition. Non-stoichiometric O-acetylation of the terminal α-l -Rha p (∼50%) was found. The outer core represents the missing glycosyl sequence in R. leguminosarum 24 LPS.