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1.
Nazarenko EL Perepelov AV Shevchenko LS Daeva ED Ivanova EP Shashkov AS Widmalm G 《Biochemistry. Biokhimii?a》2011,76(7):791-796
Structure of the O-specific polysaccharide chain of the lipopolysaccharide (LPS) of Shewanella japonica KMM 3601 was elucidated. The initial and O-deacylated LPS as well as a trisaccharide representing the O-deacetylated repeating
unit of the O-specific polysaccharide were studied by sugar analysis along with 1H and 13C NMR spectroscopy. The polysaccharide was found to contain a rare higher sugar, 5,7-diacetamido-3,5,7,9-tetradeoxy-d-glycero-d-talo-non-2-ulosonic acid (a derivative of 4-epilegionaminic acid, 4eLeg). The following structure of the trisaccharide repeating
unit was established: →4)-α-4eLegp5Ac7Ac-(2→4)-β-d-GlcpA3Ac-(1→3)-β-d-GalpNAc-(1→. 相似文献
2.
Carvalho de Souza A Ganchev DN Snel MM van der Eerden JP Vliegenthart JF Kamerling JP 《Glycoconjugate journal》2009,26(4):457-465
Cell aggregation in the marine sponge Microciona prolifera is mediated by a multimillion molecular-mass aggregation factor, termed MAF. Earlier investigations revealed that the cell
aggregation activity of MAF depends on two functional domains: (i) a Ca2+-independent cell-binding domain and (ii) a Ca2+-dependent proteoglycan self-interaction domain. Structural analysis of involved carbohydrate fragments of the proteoglycan
in the self-association established a sulfated disaccharide β-d-GlcpNAc3S-(1→3)-α-l-Fucp and a pyruvated trisaccharide β-d-Galp4,6(R)Pyr-(1→4)-β-d-GlcpNAc-(1→3)-α-l-Fucp. Recent UV, SPR, and TEM studies, using BSA conjugates and gold nanoparticles of the synthetic sulfated disaccharide, clearly
demonstrated self-recognition on the disaccharide level in the presence of Ca2+-ions. To determine binding forces of the carbohydrate–carbohydrate interactions for both synthetic MAF oligosaccharides,
atomic force microscopy (AFM) studies were carried out. It turned out that, in the presence of Ca2+-ions, the force required to separate the tip and sample coated with a self-assembling monolayer of thiol-spacer-containing
β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH2)3S(CH2)6S- was found to be quantized in integer multiples of 30 ± 6 pN. No binding was observed between the two monolayers in the
absence of Ca2+-ions. Cd2+-ions could partially induce the self-interaction. In contrast, similar AFM experiments with thiol-spacer-containing β-d-Galp4,6(R)Pyr-(1→4)-β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH2)3S(CH2)6S- did not show a binding in the presence of Ca2+-ions. Also TEM experiments of gold nanoparticles coated with the pyruvated trisaccharide could not make visible aggregation
in the presence of Ca2+-ions. It is suggested that the self-interaction between the sulfated disaccharide fragments is stronger than that between
the pyruvated trisaccharide. 相似文献
3.
Lipopolysaccharides (LPSs) of two strains Pragia fontium 97U116 and 27480 were isolated and characterized; they were close to those of other representatives of the family Enterobacteriaceae in fatty acid composition and contained, respectively, 3-hydroxytetradecanoic acid as the predominant component (45.8 and 45.1%), tetradecanoic (23.5 and 28.9%), hexadecanoic (12.6 and 7.9%), hexadecenoic (12.6 and 7.9%), and dodecanoic (4.9 and 4.2%) fatty acids. The O-specific polysaccharides consisted of linear penta- and tetrasaccharide repeating units: →2)-α-D-Galf-(1→3)-α-L-Rhap2Ac-(1→4)-α-D-GlcpNAc-(1→2)-α-L-Rhap-(1→3)-β-D-GlcpNAc-(1→ →4)-β-D-ManpNAc3NAcA-(1→2)-α-L-Rhap-(1→3)-β-L-Rhap-(1→4)-α-D-GlcpNAc-(1→ The LPSs of P. fontium 97U116 and 27480 were serologically active and belonged to different serogroups; they were less toxic than those of strain E. coli O55:B5, but more pyrogenic than the Pyrogenal preparation. 相似文献
4.
l-threo-3,4-Dihydroxyphenylserine (DOPS) is a chiral unnatural β-hydroxy amino acid used for the treatment of Parkinson disease.
We developed a continuous bioconversion system for DOPS production that uses whole-cell biocatalyst of recombinant Escherichia coli expressing l-threonine aldolase (l-TA) genes cloned from Streptomyces avelmitilis MA-4680. Maximum conversion rates were observed at 2 M glycine, 145 mM 3,4-dihydroxybenzaldehyde, 0.75% Triton-X, 5 g E. coli cells/l, pH 6.5 and 10°C. In the optimized condition, overall productivity was 8 g/l, which represents 40 times the synthesis
yield possible with no optimization of conditions. 相似文献
5.
Elin Säwén Eine Huttunen Xue Zhang Zhennai Yang Göran Widmalm 《Journal of biomolecular NMR》2010,47(2):125-134
The use of lactic acid bacteria in fermentation of milk results in favorable physical and rheological properties due to in
situ exopolysaccharide (EPS) production. The EPS from S. thermophilus ST1 produces highly viscous aqueous solutions and its structure has been investigated by NMR spectroscopy. Notably, all aspects
of the elucidation of its primary structure including component analysis and absolute configuration of the constituent monosaccharides
were carried out by NMR spectroscopy. An array of techniques was utilized including, inter alia, PANSY and NOESY-HSQC TILT
experiments. The EPS is composed of hexasaccharide repeating units with the following structure: → 3)[α-d-Glcp-(1 → 4)]-β-d-Galp-(1 → 4)-β-d-Glcp-(1 → 4)[β-d-Galf-(1 → 6)]-β-d-Glcp-(1 → 6)-β-d-Glcp-(1 →, in which the residues in square brackets are terminal groups substituting backbone sugar residues that consequently
are branch-points in the repeating unit of the polymer. Thus, the EPS consists of a backbone of four sugar residues with two
terminal sugar residues making up two side-chains of the repeating unit. The molecular mass of the polymer was determined
using translational diffusion experiments which resulted in Mw = 62 kDa, corresponding to 64 repeating units in the EPS. 相似文献
6.
Van Laere KM Hartemink R Beldman G Pitson S Dijkema C Schols HA Voragen AG 《Applied microbiology and biotechnology》1999,52(5):681-688
Bifidobacterium adolescentis, a gram-positive saccharolytic bacterium found in the human colon, can, alongside other bacteria, utilise stachyose in vitro
thanks to the production of an α-galactosidase. The enzyme was purified from the cell-free extract of Bi. adolescentis DSM 20083T. It was found to act with retention of configuration (α→α), releasing α-galactose from p-nitrophenyl galactoside. This hydrolysis probably operates with a double-displacement mechanism, and is consistent with the
observed glycosyltransferase activity. As α-galactosides are interesting substrates for bifidobacteria, we focused on the
production of new types of α-galactosides using the transgalactosylation activity of Bi. adolescentisα-galactosides. Starting from melibiose, raffinose and stachyose oligosaccharides could be formed. The transferase activity
was highest at pH 7 and 40 °C. Starting from 300 mM melibiose a maximum yield of 33% oligosaccharides was obtained. The oligosaccharides
formed from melibiose were purified by size-exclusion chromatography and their structure was elucidated by NMR spectroscopy
in combination with enzymatic degradation and sugar linkage analysis. The trisaccharide α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp and tetrasaccharide α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp were identified, and this indicates that the transgalactosylation to melibiose occurred selectively at the C-6 hydroxyl group
of the galactosyl residue. The trisaccaride α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp formed could be utilised by various intestinal bacteria, including various bifidobacteria, and might be an interesting pre-
and synbiotic substrate.
Received: 15 March 1999 / Received revision: 8 June 1999 / Accepted: 11 June 1999 相似文献
7.
Diastereoselectivity-enhanced mutants of l-threonine aldolase (l-TA) for l-threo-3,4-dihydroxyphenylserine (l-threo-DOPS) synthesis were isolated by error-prone PCR followed by a high-throughput screening. The most improved mutant was achieved
from the mutant T3-3mm2, showing a 4-fold increase over the wild-type l-TA. When aldol condensation activity was examined using whole cells of T3-3mm2, its de was constantly maintained at 55% during
the batch reactions for 80 h, yielding 3.8 mg l-threo-DOPS/ml. 相似文献
8.
Andrei V. Perepelov Nina A. Kocharova Yuriy A. Knirel Per-Erik Jansson Andrej Weintraub 《Carbohydrate research》2011,346(3):1951
The O-polysaccharide of Vibriocholerae O43 was studied using chemical analyses, triflic acid solvolysis and 2D NMR spectroscopy, including 1H/1H COSY, TOCSY, NOESY and 1H/13C gradient-selected HSQC experiments. The following structure of the tetrasaccharide repeating unit of the polysaccharide was established:→3)-β-d-Quip4NAcyl-(1→3)-α-d-GalpNAcA-(1→4)-α-d-GalpNAc-(1→3)-α-d-QuipNAc-(1→where d-QuiNAc stands for 2-acetamido-2,6-dideoxy-d-glucose, d-Qui4NAcyl for 4-(N-acetyl-l-allothreonyl)amino-4,6-dideoxy-d-glucose and d-GalNAcA for 2-acetamido-2-deoxy-d-galacturonic acid. 相似文献
9.
Employing a photoaffinity labeling procedure with 8-azido-S-adenosyl-l-[methyl-3H]methionine (8-N3-Ado[methyl-3H]Met), the binding sites for S-adenosyl-l-methionine (AdoMet) of three protein N-methyltransferases [AdoMet:myelin basic protein-arginine N-methyltransferase (EC2.1.1.23); AdoMet:histone-arginin N-methyltransferase (EC2.1.1.23); and AdoMet:cytochromec-lysine N-methyltransferase (EC2.1.1.59)] have been investigated. The incorporation of the photoaffinity label into the enzymes upon UV irradiation was highly specific. In order to define the AdoMet binding sites, the photolabeled enzymes were sequentially digested with trypsin, chymotrypsin, and endoproteinase Glu-C. After each proteolytic digestion, radiolabeled peptide from each enzyme was resolved on HPLC first by gradient elution and further purified by an isocratic elution. Retention times of the purified radiolabeled peptides from the three enzymes from the corresponding proteolysis were significantly different, indicating that their sizes and compositions were different. Amino acid composition analysis of these peptides confirmed further that the AdoMet binding sites of these protein N-methyltransferases are quite different. 相似文献
10.
Olga A. Valueva Evelina L. Zdorovenko Vadim V. Kachala Liudmyla D. Varbanets Nikolay P. Arbatsky Vladimir V. Shubchynskyy Alexander S. Shashkov Yuriy A. Knirel 《Carbohydrate research》2011,(1):146
The following structure of the O-polysaccharide of Pragia fontium 27480 was elucidated by sugar analysis, including determination of the absolute configurations of the monosaccharides, and Smith degradation along with 1D and 2D 1H and 13C NMR spectroscopy:→4)-β-d-ManpNAc3NAcA-(1→2)-α-l-Rhap-(1→3)-β-l-Rhap-(1→4)-α-d-GlcpNAc-(1→where ManNAc3NAcA stands for 2,3-diacetamido-2,3-dideoxymannuronic acid. 相似文献
11.
Jonathan A. Lindquist Elisabeth Barofsky Philip N. McFadden 《Journal of Protein Chemistry》1996,15(1):115-122
Protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase (PCM, E.C. 2.1.1.77) was previously shown to be enzymatically methyl esterified in an autocatalytic manner at altered aspartyl residues; methyl esters are observed in a subpopulation of the enzyme termed thePCM fraction [Lindquist and McFadden (1994),J. Protein Chem.
13, 23–30]. The altered aspartyl sites serving as methyl acceptors inPCM have now been localized by using proteolytic enzymes and chemical cleavage techniques in combination with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to identify fragments of the [3H]automethylated enzyme that contain a [3H]methyl ester. Methylation was positively identified at positions Asn188 and Asp217 in the enzyme sequence, a consequence of the spontaneous alteration of these sites tol-isoaspartyl ord-aspartyl sites and their methylation by active PCM molecules. The identification of more than one site of automethylation shows thatPCM is not a homogeneous population of damaged PCM molecules, but rather a complex population of molecules with a variety of age-altered damage sites.Abbreviations PCM
protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase
- EDTA
disodium ethylenediaminetetraacetate
- PMSF
phenylmethylsulfonyl fluoride
- TEA
trifluoroacetic acid
- HPLC
high-pressure liquid chromatography 相似文献
12.
Lactococcus lactis subspecies cremoris SBT 0495 produces the phosphopolysaccharide viilian, which consists of the repeating unit β-d-glucosyl-(1→4)-(α-l-rhamnosyl-(1→2))-(α-d-galactose-1-phosphoryl-(→3)-β-galactosyl-(1→4)-β-d-glucose. A lipid extract was prepared from cells in the late exponential phase of growth and was hydrolyzed by hydrochloric
acid under mild conditions to split lipid-linked intermediates in the extract into lipid and sugar moieties. Both moieties
were purified by chromatographic techniques and were characterized to identify intermediates of the viilian biosynthetic pathway.
A polyisoprenoid isolated from the chloroform-soluble fraction of the hydrolyzed lipid extract was identified by mass spectrometry
as undecaprenol. Saccharides isolated from the water-soluble fraction of the hydrolyzed lipid extract by anion-exchange chromatography,
were characterized by glycosidic linkage analysis to discriminate sugar moieties of intermediates of viilian biosynthesis
from compounds liberated from cell wall components. Some oligosaccharide analogues contain a glycerol residue, suggesting
that these are fragments of glycosylglycerides and/or lipoteichoic acid. Three fragments were identified to be glucose, galactosyl-(1→4)-glucose,
and rhamnosyl-(1→2)-galactosyl-(1→4)-glucose, which are in agreement with the structure of the repeating unit of viilian.
These saccharides most likely represent the first three steps of the sequential assembly of the repeating unit of the undecaprenol
assembly.
Received: 2 November 1998 / Accepted: 3 March 1999 相似文献
13.
A question that is central to understanding the mechanisms of aging and cellular deterioration is whether enzymes involved in recognition and metabolism of spontaneously damaged proteins are themselves damaged, either becoming substrates for their own activity; or being unable to act upon themselves, initiating cascades of cellular damage. We show here byin vitro experiments that protein (d-aspartyl/l-isoaspartyl) carboxyl methyltransferase (PCM) from bovine erythrocytes does methylate age-dependent amino acid damage in its own sequence. The subpopulation that is methylated, termed thePCM fraction, appears to be formed through age-dependent deamidation of an asparaginyl site to either anl-isoaspartyl ord-aspartyl site because (a) the stoichiometry of automethylation of purified PCM is less than 1%, a value typical of the substoichiometric methylation of many other aged protein substrates, (b)PCM is slightly more acidic than the bulk of PCM, and (c) the methyl esterified site inPCM has the characteristic base-lability of this type of methyl ester. Also, the methyl group is not incorporated into the enzyme as an active site intermediate because the incorporated methyl group is not chased onto substrate protein. The effect of enzyme dilution on the rate of the automethylation reaction is consistent with methylation occurring between protein molecules, showing that the pool of PCM is autocatalytic even though individual molecules may not be. The automethylation and possible self-repair of the PCM pool has implications for maintaining thein vivo efficiency of methylation-dependent protein repair. 相似文献
14.
Kilian Dill R. Douglas Carter Jean M. Lacombe André A. Pavia 《Journal of Protein Chemistry》1985,4(6):363-373
13C-NMR spectral data are presented for four neuropeptides composed ofl-Asp, Ac-l-Asp, andd-Glu, which contain and peptide linkages. The data for the various compounds are compared to related dipeptides, one of which is a known neuropeptide, in order to gain structural information about these compounds. Electron-nuclear relaxation rates were used to elucidate the metal-ion binding sites of these species. 相似文献
15.
In the present study we have investigated the effect of exogenous cyclitols on accumulation of their galactosides and raffinose
family oligosaccharides (RFOs) in maturing smooth tare (Vicia tetrasperma [L.] Schreb) seeds. Feeding d-pinitol to pods of smooth tare increased the amount of free d-pinitol and its galactosides: galactopinitol A, galactopinitol B, di- and trigalactopinitol A in seeds. Similarly, feeding
d-chiro-inositol, which does not occur naturally in Vicia seeds, resulted in the transport of this cyclitol in the seed, and caused accumulation of high levels of d-chiro-inositol galactosides (fagopyritol B1, B2 and B3). Accumulation of both cyclitols and their galactosides drastically reduced
accumulation of verbascose and, to a lesser extent, stachyose and di-galactosyl- myo-inositol. Feeding d-chiro-inositol also decreased accumulation of di- and tri-galactosyl pinitols, naturally occurring in seeds. Inhibition of RFOs
accumulation by elevated levels of free cyclitols indicates competition between biosynthesis of both types galactosides, and
similarity of both biosynthetic pathways in smooth tare seeds. 相似文献
16.
Monoclonal antibodies were raised against rhamnogalacturonan I backbone, a pectin domain, using Arabidopsis thaliana seed mucilage-derived rhamnogalacturonan I oligosaccharides—BSA conjugates. Two monoclonal antibodies, designated INRA-RU1
and INRA-RU2, selected for further characterization, were specific for the backbone of rhamnogalacturonan I, displaying no
binding activity against the other pectin domains i.e. homogalacturonans, galactans or arabinans. A range of oligosaccharides
was prepared by enzymatic digestion of rhamnogalacturonan I isolated from Arabidopsis thaliana seed mucilage and from sugar beet pectin, purified by low-pressure chromatography and characterized by high-performance anion-exchange
chromatography and mass spectrometry. These rhamnogalacturonan I oligomers were used to characterize the binding site of the
two monoclonal antibodies by competitive inhibition. Both INRA-RU1 and INRA-RU2 showed maximal binding to the [→2)-α-l-rhamnosep-(1→4)-α-d-galacturonic acid p-(1→]7 structural motif but differed in their minimum binding requirement. INRA-RU2 required at least two disaccharide (rhamnose–galacturonic
acid) repeats for the antibody to bind, while INRA-RU1 required a minimum of six disaccharide repeats. Furthermore, the binding
capacity of INRA-RU1 decreased steeply as the number of disaccharide repeats go beyond seven. Each of these antibodies reacted
with hairy regions isolated from sugar beet pectin. Immunofluorescence microscopy indicated that both antibodies can be readily
used to detect rhamnogalacturonan I epitopes in various cell wall samples. 相似文献
17.
The rumen anaerobic fungusPiromonas communis, unlike the rumen anaerobic fungiNeocallimastix frontalis andNeocallimastix patriciarum, produced extracellular α-(4-O-methyl)-d-glucuronidase when grown in cultures containing filter-paper, barley straw, birchwood xylan or birchwood sawdust as carbon
source. The highest concentration of enzyme was produced in cultures containing birchwood sawdust. The aldobiouronic acidO-α-(4-O-methyl-d-glucopyran-osyluronic acid)-(1 → 2)-d-xylopyranose (MeGlcAXyl) was the best substrate of those tested: the aldotriouronic acidO-α-(4-O-methyl-d-glucopyranosyluronic acid (1 → 2)-O-\-d-xylopyranosyl-(1 → 4)-d-xylopyranose (MeGlcAXyl2) and the aldotetraouronic acidO-α-(4-O-methyl-d-glucopyranosyluronic acid)-(1 → 2)-O-\-d-xylopyranosyl-(1 → 4)-O-\-d-xylopyranosyl-(1 → 4)-d-xylopyranose (MeGlcAXyl3) were also attacked but the rate fell as the degree of polymerisation increased. When the same substituted xylooligosaccharides
were reduced to the corresponding alditols the enzyme activity disappeared. Similarly,p-nitrophenyl-α-d-glucuronide was not a substrate. Remarkably, the relative rates of attack shown by the α-(4-O-methyl)-d-glucuronidase on the aldouronic acids and on xylans extracted from birchwood, oat spelts and oat straw differed according
to the carbon source used to produce the enzyme. The α-(4-O-methyl)-d-glucuronidase had a pH optimum of 5.5 and a temperature optimum of 50°C. On gel filtration the enzyme was shown to be associated
with proteins covering the range 100–300 kDa, but a major peak of activity in the column effluent appeared to have a molecular
mass of 103 kDa. 相似文献
18.
Feng B Hu W Ma BP Wang YZ Huang HZ Wang SQ Qian XH 《Applied microbiology and biotechnology》2007,76(6):1329-1338
It has been previously reported that a glucoamylase from Curvularia lunata is able to hydrolyze the terminal 1,2-linked rhamnosyl residues of sugar chains at C-3 position of steroidal saponins. In
this work, the enzyme was isolated and identified after isolation and purification by column chromatography including gel
filtration and ion-exchange chromatography. Analysis of protein fragments by MALDI-TOF/TOF™ proteomics Analyzer indicated
the enzyme to be 1,4-alpha-D-glucan glucohydrolase EC 3.2.1.3, GA and had considerable homology with the glucoamylase from Aspergillus oryzae. We first found that the glucoamylase was produced from C. lunata and was able to hydrolyze the terminal rhamnosyl of steroidal saponins. The enzyme had the general character of glucoamylase,
which hydrolyze starch. It had a molecular mass of 66 kDa and was optimally active at 50°C, pH 4, and specific activity of
12.34 U mg of total protein−1 under the conditions, using diosgenin-3-O-α-L-rhamnopyranosyl(1→4)-[α-L-rhamnopyranosyl (1→2)]-β-D-glucopyranoside (compound II) as the substrate. Furthermore, four kinds of commercial glucoamylases from Aspergillus niger were investigated in this work, and they had the similar activity in hydrolyzing terminal rhamnosyl residues of steroidal
saponin.
This project was supported by the National Natural Science Foundation of China (NSFC; 30572333). 相似文献
19.
An DS Cui CH Sung BH Yang HC Kim SC Lee ST Im WT Kim SG 《Applied microbiology and biotechnology》2012,94(3):673-682
The gene encoding an α-l-arabinofuranosidase that could biotransform ginsenoside Rc {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-[α-l-arabinofuranosyl-(1–6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to ginsenoside Rd {3-O-[β-d-glucopyranosyl-(1–2)-β-d-glucopyranosyl]-20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol} was cloned from a soil bacterium, Rhodanobacter ginsenosidimutans strain Gsoil 3054T, and the recombinant enzyme was characterized. The enzyme (AbfA) hydrolyzed the arabinofuranosyl moiety from ginsenoside
Rc and was classified as a family 51 glycoside hydrolase based on amino acid sequence analysis. Recombinant AbfA expressed
in Escherichia coli hydrolyzed non-reducing arabinofuranoside moieties with apparent K
m values of 0.53 ± 0.07 and 0.30 ± 0.07 mM and V
max values of 27.1 ± 1.7 and 49.6 ± 4.1 μmol min−1 mg−1 of protein for p-nitrophenyl-α-l-arabinofuranoside and ginsenoside Rc, respectively. The enzyme exhibited preferential substrate specificity of the exo-type
mode of action towards polyarabinosides or oligoarabinosides. AbfA demonstrated substrate-specific activity for the bioconversion
of ginsenosides, as it hydrolyzed only arabinofuranoside moieties from ginsenoside Rc and its derivatives, and not other sugar
groups. These results are the first report of a glycoside hydrolase family 51 α-l-arabinofuranosidase that can transform ginsenoside Rc to Rd. 相似文献
20.
Xiaomin Li Andrei V. Perepelov Sof’ya N. Senchenkova Sergei D. Shevelev Alexander S. Shashkov Lei Wang Yuriy A. Knirel 《Carbohydrate research》2010,345(11):1581-1587
The O-antigen is an essential component of lipopolysaccharide on the surface of Gram-negative bacteria and plays an important role in its pathogenicity. Composition and structure of the O-antigens of Escherichia coli are highly diverse mainly due to genetic variations in the O-antigen gene cluster. In this work, the chemical structure and the gene cluster of the O-antigen of E. coli O161 were studied. Chemical degradations, sugar analyses, and NMR spectroscopy showed that the O161 antigen possesses a trisaccharide O-repeating unit containing a 5-N-acetyl-7-N-(d-alanyl) derivative of 5,7-diamino-3,5,7,9-tetradeoxy-d-glycero-d-galacto-non-2-ulosonic (legionaminic) acid (Leg5Ac7Ala) and having the following structure:
→8)-α-Legp5Ac7Ala-(2→4)-β-d-GlcpA-(1→3)-β-d-GlcpNAc-(1→ 相似文献