Galacturonosyltransferases (GalATs) are required for the synthesis of pectin, a family of complex polysaccharides present in the cell walls of all land plants. We report the identification of a pectin GalAT (GAUT1) using peptide sequences obtained from Arabidopsis thaliana proteins partially purified for homogalacturonan (HG) ␣-1,4-GalAT activity. Transient expression of GAUT1 cDNA in the human embryonic kidney cell line HEK293 yielded uridine diphosphogalacturonic acid:GalAT activity. Polyclonal antibodies generated against GAUT1 immunoabsorbed HG ␣-1,4-GalAT activity from Arabidopsis solubilized membrane proteins. BLAST analysis of the Arabidopsis genome identified a family of 25 genes with high sequence similarity to GAUT1 and homologous genes in other dicots, in rice, and in Physcomitrella. Sequence alignment and phylogenetic Bayesian analysis of the Arabidopsis GAUT1-related gene family separates them into four related clades of GAUT and GAUT-like genes that are distinct from the other Arabidopsis members of glycosyltransferase family 8. The identification of GAUT1 as a HG GalAT and of the GAUT1-related gene family provides the genetic and biochemical tools required to study the function of these genes in pectin synthesis.biosynthesis ͉ cell wall ͉ glycosyltransferase ͉ polygalacturonic acid ͉ pectic polysaccharide

Fresh and 3-day-old coffee pulp of the Arabica variety were analyzed for polyphenol composition followed by characterization by two different methods. The first method consisted in subjecting coffee pulp powder to direct thiolysis. For the second method, coffee pulp was subjected to successive solvent extractions, followed by thiolysis. Quantification of phenolic compounds was then achieved by high-performance liquid chromatography (HPLC) analysis of thiolysis products. Four major classes of polyphenols were identified: flavan-3-ols (monomers and procyanidins), hydroxycinnamic acids, flavonols, and anthocyanidins. Differences in concentration of procyanidins were observed between fresh and 3-day-old coffee pulp. Constitutive units were mainly epicatechin, representing more than 90% of the proanthocyanidin units, with average degrees of polymerization in the range of 3.8-9.1. Monomer to hexamer units of flavan-3-ols from fresh coffee pulp were separated by normal-phase HPLC. Molecular size of oligomeric proanthocyanidins was obtained by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Results obtained confirm the presence of oligomers of the flavan-3-ol (-)-epicatechin.

No abstract

SummaryA basic, 51 kDa protein was puri®ed from suspension-cultured tomato and shown to inhibit the hydrolytic activity of a xyloglucan-speci®c endoglucanase (XEG) from the fungus Aspergillus aculeatus. The tomato (Lycopersicon esculentum) protein, termed XEG inhibitor protein (XEGIP), inhibits XEG activity by forming a 1 : 1 protein:protein complex with a K i % 0.5 nM. To our knowledge, XEGIP is the ®rst reported proteinaceous inhibitor of any endo-b-1,4-glucanase, including the cellulases. The cDNA encoding XEGIP was cloned and sequenced. Database analysis revealed homology with carrot extracellular dermal glycoprotein (EDGP), which has a putative role in plant defense. XEGIP also has sequence similarity to ESTs from a broad range of plant species, suggesting that XEGIP-like genes are widely distributed in the plant kingdom. Although Southern analysis detected only a single XEGIP gene in tomato, at least ®ve other XEGIP-like tomato sequences have been identi®ed. Similar small families of XEGIP-like sequences are present in other plants, including Arabidopsis. XEGIP also has some sequence similarity to two previously characterized proteins, basic globulin 7S protein from soybean and conglutin c from lupin. Several amino acids in the XEGIP sequence, notably 8 of the 12 cysteines, are generally conserved in all the XEGIP-like proteins we have encountered, suggesting a fundamental structural similarity. Northern analysis revealed that XEGIP is widely expressed in tomato vegetative tissues and is present in expanding and maturing fruit, but is downregulated during ripening.

Lipopolysaccharides (LPS) and capsular polysaccharides (K antigens) may influence the interaction of rhizobia with their specific hosts; therefore, we conducted a comparative analysis of Sinorhizobium fredii and Sinorhizobium meliloti, which are genetically related, yet symbiotically distinct, nitrogen-fixing microsymbionts of legumes. We found that both species typically produce strain-specific K antigens that consist of 3-deoxy-d-manno-2-octulosonic acid (Kdo), or other 1-carboxy-2-keto-3-deoxy sugars (such as sialic acid), and hexoses. The K antigens of each strain are distinguished by glycosyl composition, anomeric configuration, acetylation, and molecular weight distribution. One consistent difference between the K antigens ofS. fredii and those of S. meliloti is the presence of N-acetyl groups in the polysaccharides of the latter. In contrast to the K antigens, the LPS ofSinorhizobium spp. are major common antigens. Rough (R) LPS is the predominant form of LPS produced by cultured cells, and some strains release almost no detectable smooth (S) LPS upon extraction.Sinorhizobium spp. are delineated into two major RLPS core serogroups, which do not correspond to species (i.e., host range). The O antigens of the SLPS, when present, have similar degrees of polymerization and appear to be structurally conserved throughout the genus. Interestingly, one strain was found to be distinct from all others: S. fredii HH303 produces a unique K antigen, which contains galacturonic acid and rhamnose, and the RLPS did not fall into either of the RLPS core serogroups. The results of this study indicate that the conserved S- and RLPS of Sinorhizobiumspp. lack the structural information necessary to influence host specificity, whereas the variable K antigens may affect strain-cultivar interactions.

"Energy-resolved collision-induced dissociation pathways of model N-linked glycopeptides: implications for capturing glycan connectivity and peptide sequence in a single experiment" (2014). Faculty Publications --Chemistry Department. 68. http://digitalcommons.unl.edu/chemfacpub/68Energy-resolved collision-induced dissociation pathways of model N-linked glycopeptides: implications for capturing glycan connectivity and peptide sequence in a single experiment † Venkata Kolli and Eric D. Dodds * Tandem mass spectrometry (MS/MS) of glycopeptides stands among the principal analytical approaches for assessing protein glycosylation in a site-specific manner. The aims of such experiments are often to determine the monosaccharide connectivity of the glycan, the amino acid sequence of the peptide, and the site of glycan attachment. This level of detail is often difficult to achieve using any single ion dissociation method; however, precedent does exist for use of collision-induced dissociation (CID) to establish either the connectivity of the oligosaccharide or the sequence of the polypeptide depending upon the applied collision energy. Unfortunately, the relative energy requirements for glycan and peptide cleavage have not been thoroughly characterized with respect to specific physicochemical characteristics of the precursor ions. This report describes case studies on the energy-resolved CID pathways of model tryptic glycopeptides derived from Erythrina cristagalli lectin and bovine ribonuclease B. While glycopeptide ions having disparate physical and chemical characteristics shared strikingly similar qualitative responses to increasing vibrational energy deposition, the absolute collision energies at which either glycan or peptide fragmentations were accessed varied substantially among the precursor ions examined. Nevertheless, these data suggest that the energy requirements for peptide and glycan cleavage may be somewhat predictable based on characteristics of the precursor ion. The practical usefulness of these observations was demonstrated through implementation of online collision energy modulation such that both glycan and peptide fragmentation were captured in the same spectrum, providing near-exhaustive glycopeptide characterization in a single experiment. Overall, these results highlight the potential to further extend the capabilities of CID in the context of glycoproteomics.

Nontypeable Haemophilus influenzae (NTHi) is an important pathogen responsible for otitis media in children and of pneumonitis in adults with depressed resistance. NTHi is acapsular and, therefore, capsular polysaccharide-based vaccines are ineffective for preventing infections by this pathogen. Recently it was found that a detoxified lipooligo-saccharide (LOS) conjugate from NTHi 9274 induced bactericidal antibodies effective against a large number of NTHi isolates, and conferred protection against NTHi otitis media in chinchillas (X.-X.Gu et al., 1996, Infect. Immun.,64, 4047-4053; X. -X.Gu et al., 1997., Infect. Immun.,65, 4488-4493). In this paper we report the chemical character-ization of the LOS from NTHi 9274 LOS. NTHi is capable of expressing a heterogenous population of LOS exhibited by multiple oligosaccharide (OS) epitopes. OSs released from the LOS of NTHi 9274 by mild acid hydrolysis were purified using Bio-Gel P4 gel permeation chromatography. The OSs were characterized by glycosyl composition analysis, glycosyl linkage analysis, nuclear magnetic resonance spectroscopy (NMR), fast atom bombardment mass spectro-metry (FAB-MS), matrix-assisted laser desorption time of flight mass spectro-metry (MALDITOF-MS), and tandem MS/MS. At least 17 different OS molecules were observed. These contained variable glycosyl residues, phosphate (P), and phospho-ethanolamine (PEA) substituents. These molecules contained either three, four, or five hexoses, and all contained four heptosyl residues. The four heptosyl residues consisted of one D,D-Hep and three L,D-Hep. Dephosphorylation of the OSs with aqueous 48% hydrofluoric acid (HF) reduced the number of molecules to about to seven; Hex(1)-(7)Hep(4)Kdo(1). Of these seven, Hex(2)Hep(4)Kdo(1), Hex(3)Hep(4)Kdo(1), and Hex(4)Hep(4)Kdo(1)were the major constituents. Thus, this NTHi LOS preparation is very heterogeneous, and contains structures different from those previously published for Haemophilus influenzae. The tandem MS/MS analysis and glycosyl linkage data suggest that the LOS oligosaccharides have the following structures where Hex is either a Glc or Gal residue.

The α-chain of the core oligosaccharide of the lipo-oligosaccharide (LOS) produced by Neisseria gonorrhoeae can undergo reversible and rapid changes in structure due to phase-variable production of certain enzymes employed in the biosynthesis of the lacto- N-neotetraose structure. Five of these enzymes are encoded by the lgtABCDE operon, and polynucleotide tracts within three of these genes ( lgtA, lgtC and lgtD) can be substrates for slipped-strand mispairing events that lead to nucleotide insertions or deletion events which result in variable production of their respective gene products. We now report that phase-variable synthesis of the lgtA and lgtC gene products in strain FA19 results in the production of elongated LOS α-chains and that the presence of these LOS species can result in gonococci being sensitive to the bacteriolytic action of serum-antibody and complement. Hence, phase variation within the lgtABCDE operon can significantly impact the ability of gonococci to subvert this important host defense system.