Stability of Curcuma longa rhizome lectin: Role of N-linked glycosylation
Curcuma longa rhizome lectin, a mannose-binding protein of non-seed portions of turmeric, is known to have antifungal, antibacterial and α-glucosidase inhibitory activities. We studied the role of complex-type glycans attached to asparagine (Asn) 66 and Asn 110 to elucidate the role of carbohydrates in lectin activity and stability. Apart from the native lectin, the characteristics of a deglycosylated Escherichia coli expressed lectin, high-mannose oligosaccharides at both asparagines and its glycosylation mutants N66Q and N110Q expressed in Pichia pastoris, were compared to understand the relationship between glycos...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Biswas, H., Chattopadhyaya, R. Tags: Structural Biology Source Type: research
Functional analysis of N-linking oligosaccharyl transferase enzymes encoded by deep-sea vent proteobacteria
Bacterial N-linking oligosaccharyl transferases (OTase enzymes) transfer lipid-linked glycans to selected proteins in the periplasm and were first described in the intestinal pathogen Campylobacter jejuni, a member of the -proteobacteria-subdivision of bacteria. More recently, orthologues from other -proteobacterial Campylobacter and Helicobacter species and a -proteobacterium, Desulfovibrio desulfuricans, have been described, suggesting that these two subdivisions of bacteria may be a source of further N-linked protein glycosylation systems. Whole-genome sequencing of both - and -proteobacteria from deep-sea vent habitats...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Mills, D. C., Jervis, A. J., Abouelhadid, S., Yates, L. E., Cuccui, J., Linton, D., Wren, B. W. Tags: Microbial Biology Source Type: research
Comprehensive analysis of flagellin glycosylation in Campylobacter jejuni NCTC 11168 reveals incorporation of legionaminic acid and its importance for host colonization
Campylobacter jejuni is the leading cause of bacterial gastroenteritis. It relies on several virulence factors for host colonization, including glycosylated flagella. C. jejuni NCTC 11168 modifies its flagellins with pseudaminic acid derivatives. It is also presumed to modify these proteins with legionaminic acid, although no glycopeptide evidence was available at the onset of this study. The enzyme encoded by cj1319 can be used to make legionaminic acid in vitro, but the pathway for legionaminic acid synthesis partially inferred by knockout mutagenesis in Campylobacter coli VC167 excludes Cj1319. To address this contradic...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Zebian, N., Merkx-Jacques, A., Pittock, P. P., Houle, S., Dozois, C. M., Lajoie, G. A., Creuzenet, C. Tags: Microbial Biology Source Type: research
Size product modulation by enzyme concentration reveals two distinct levan elongation mechanisms in Bacillus subtilis levansucrase
Two levan distributions are produced typically by Bacillus subtilis levansucrase (SacB): a high-molecular weight (HMW) levan with an average molecular weight of 2300 kDa, and a low-molecular weight (LMW) levan with 7.2 kDa. Previous results have demonstrated how reaction conditions modulate levan molecular weight distribution. Here we demonstrate that the SacB enzyme is able to perform two mechanisms: a processive mechanism for the synthesis of HMW levan and a non-processive mechanism for the synthesis of LMW levan. Furthermore, the effect of enzyme and substrate concentration on the elongation mechanism was studied. While...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Raga-Carbajal, E., Carrillo-Nava, E., Costas, M., Porras-Dominguez, J., Lopez-Munguia, A., Olvera, C. Tags: Glycan Synthesis Source Type: research
Mucin-type O-glycosylation is controlled by short- and long-range glycopeptide substrate recognition that varies among members of the polypeptide GalNAc transferase family
A large family of UDP-GalNAc:polypeptide GalNAc transferases (ppGalNAc-Ts) initiates and defines sites of mucin-type Ser/Thr-O-GalNAc glycosylation. Family members have been classified into peptide- and glycopeptide-preferring subfamilies, although both families possess variable activities against glycopeptide substrates. All but one isoform contains a C-terminal carbohydrate-binding lectin domain whose roles in modulating glycopeptide specificity is just being understood. We have previously shown for several peptide-preferring isoforms that the presence of a remote Thr-O-GalNAc, 6–17 residues from a Ser/Thr acceptor...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Revoredo, L., Wang, S., Bennett, E. P., Clausen, H., Moremen, K. W., Jarvis, D. L., Ten Hagen, K. G., Tabak, L. A., Gerken, T. A. Tags: Glycan Synthesis Source Type: research
Mechanisms of the sialidase and trans-sialidase activities of bacterial sialyltransferases from glycosyltransferase family 80
Many important biological functions are mediated by complex glycan structures containing the nine-carbon sugar sialic acid (Sia) at terminal, non-reducing positions. Sia are introduced onto glycan structures by enzymes known as sialyltransferases (STs). Bacterial STs from the glycosyltransferase family GT80 are a group of well-studied enzymes used for the synthesis of sialylated glycan structures. While highly efficient at sialyl transfer, these enzymes also demonstrate sialidase and trans-sialidase activities for which there is some debate surrounding the corresponding enzymatic mechanisms. Here we propose a mechanism for...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Mehr, K., Withers, S. G. Tags: Chemical Biology Source Type: research
Hyaluronan oligomers sensitize chronic myeloid leukemia cell lines to the effect of Imatinib
Chronic myeloid leukemia is a myeloproliferative syndrome characterized by the presence of the Philadelphia chromosome (Ph), generated by a reciprocal translocation occurring between chromosomes 9 and 22 [t(9;22)(q34;q11)]. As a consequence, a fusion gene (bcr-abl) encoding a constitutively active kinase is generated. The first-line treatment consists on BCR-ABL inhibitors such as Imatinib, Nilotinib and Dasatinib. Nevertheless, such treatment may lead to the selection of resistant cells. Therefore, finding molecules that enhance the anti-proliferative effect of first-line drugs is of value. Hyaluronan oligomers (oHA) are ...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Lompardia, S. L., Diaz, M., Papademetrio, D. L., Mascaro, M., Pibuel, M., Alvarez, E., Hajos, S. E. Tags: Cancer Biology Source Type: research
Structure and gene cluster of the O-antigen of Escherichia coli O165 containing 5-N-acetyl-7-N-[(R)-3-hydroxybutanoyl]pseudaminic acid
Upon mild acid degradation of the lipopolysaccharide of Escherichia coli O165, the O-polysaccharide chain was cleaved at the glycosidic linkage of 5-N-acetyl-7-N-[(R)-3-hydroxybutanoyl]pseudaminic acid (Pse5Hb7Ac). Analysis of the resulting linear tetrasaccharide and alkali-treated lipopolysaccharide by 1H/13C 1D and 2D nuclear magnetic resonance spectroscopy enabled elucidation of the following structure of the O-polysaccharide: ->8)-α-Psep5Hb7Ac-(2 -> 6)-β-d-Galp-(1 -> 4)-β-d-Glcp-(1 -> 3)-α-d-GlcpNAc-(1->. The β-d-Galp-(1 -> 4)-β-d-Glcp-(1 -> 3)-d-GlcpNAc structural e...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Senchenkova, S. N., Zhang, Y., Perepelov, A. V., Guo, X., Shashkov, A. S., Weintraub, A., Liu, B., Widmalm, G., Knirel, Y. A. Tags: Analytical Glycobiology Source Type: research
Probing sialoglycans on fetal bovine fetuin with azido-sugars using glycosyltransferases
Sialic acids are negatively charged sugar residues commonly found on the terminal positions of most glycoproteins. They play important roles in the stability and solubility of these proteins. Due to their unique positioning, they also frequently act as receptors for various ligands, and therefore are involved in numerous cell–cell and cell–pathogen interactions. Here, using in vitro incorporation of clickable monosaccharides with various glycosyltransferases, we probed the sialoglycans on fetal bovine fetuin. The incorporated monosaccharides were detected with chemiluminescence via click chemistry in a format o...
Source: Glycobiology - February 25, 2016 Category: Biology Authors: Wu, Z. L., Huang, X., Burton, A. J., Swift, K. A. D. Tags: GLYCO-FORUM Source Type: research
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The dependence of chemokine-glycosaminoglycan interactions on chemokine oligomerization
In this study, several differentially oligomerizing chemokines (CCL2, CCL3, CCL5, CCL7, CXCL4, CXCL8, CXCL11 and CXCL12) and select oligomerization-deficient mutants were systematically characterized by surface plasmon resonance to determine their relative affinities for heparin, heparan sulfate (HS) and chondroitin sulfate-A (CS-A). Wild-type chemokines demonstrated a hierarchy of binding affinities for heparin and HS that was markedly dependent on oligomerization. These results were corroborated by their relative propensity to accumulate on cells and the critical role of oligomerization in cell presentation. CS-A was fou...
Source: Glycobiology - February 2, 2016 Category: Biology Authors: Dyer, D. P., Salanga, C. L., Volkman, B. F., Kawamura, T., Handel, T. M. Tags: Structural Biology Source Type: research
Protein O-linked glycosylation in the plant pathogen Ralstonia solanacearum
Ralstonia solanacearum is one of the most lethal phytopathogens in the world. Due to its broad host range, it can cause wilting disease in many plant species of economic interest. In this work, we identified the O-oligosaccharyltransferase (O-OTase) responsible for protein O-glycosylation in R. solanacearum. An analysis of the glycoproteome revealed that 20 proteins, including type IV pilins are substrates of this general glycosylation system. Although multiple glycan forms were identified, the majority of the glycopeptides were modified with a pentasaccharide composed of HexNAc-(Pen)-dHex3, similar to the O antigen subuni...
Source: Glycobiology - February 2, 2016 Category: Biology Authors: Elhenawy, W., Scott, N. E., Tondo, M. L., Orellano, E. G., Foster, L. J., Feldman, M. F. Tags: Microbial Biology Source Type: research
