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Identification of a Novel Glycan N-linked to the Archaellins and S-layer protein of the thermophilic methanogen, Methanothermococcus thermolithotrophicus

ABSTRACT: Motility in the Archaea domain is facilitated by a unique motility structure termed the archaellum. N-glycosylation of the major structural proteins (archaellins) is important for their subsequent incorporation into the archaellum filament. Here, we report the structure of the archaellin glycan from Methanothermococcus thermolithotrophicus, a methanogen which grows optimally at 65°C. Four archaellin genes (flaB1-4) have previously been identified. In gel digestion and LC-MS analysis revealed the identity of the upper band as FlaB1 and the lower band as FlaB3. Examination of the protein sequences for the four archaellins indicated multiple possible N-linked glycosylation sites in each. We observed using mass spectrometry that Mtc. thermolithotrophicus archaellins is posttranslationally modified at multiple sites with an N-linked branched oligosaccharide composed of 7 sugars (1414 Da). NMR analysis of the purified glycan determined the structure to be α-D-glycero-D-manno-Hep3OMe6OMe-(1-3)-[α-GalNAcA3OMe-(1-2)-]-β-Man-(1-4)-[-GalA3OMe4OAc6CMe-(1-4)--GalA-(1-2)-]-α-GalAN-(1-3)-β-GalNAc-Asn. A detailed investigation by HILIC-MS discovered the presence of several, less abundant glycan variants, related to but distinct from the main heptameric glycan. In addition, we confirmed that the S-layer protein is modified with the same heptameric glycan suggesting a common N-glycosylation pathway.

INSTRUMENT(S): Synapt MS, Q-Tof ultima

ORGANISM(S): Methanothermococcus Thermolithotrophicus Dsm 2095

TISSUE(S): Culture Condition:anaerobically-grown Cell

SUBMITTER: John Kelly

LAB HEAD: John Francis Kelly

PROVIDER: PXD019548 | Pride | 2020-10-14

REPOSITORIES: Pride

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Project description:Our studies provide direct evidence that O-glycosylation pathways play a role in the regulation of cell growth through apoptosis and proliferation pathways. Eight small molecular weight analogues of the GalNAc-alpha-1-O-serine/threonine structure based on 1-benzyl-2-acetamido-2- deoxy-alpha-O-D-galactopyranoside have been synthesised and tested in 5 human colorectal cancer cell lines. Three inhibitors, 1-benzyl-2-acetamido-2-deoxy-alpha-O-D-galactopyranoside and the corresponding 2-azido- and C-glycoside analogues, were screened in two colorectal cancer cell lines at 0.5mM and showed induction of apoptosis. Proliferation was down regulated in the same two cell lines with all three inhibitors, as detected by Ki67 staining and gene array. Treatment both cell lines with inhibitors led to changes in glycosylation detected with peanut lectin. The competitive action of the inhibitors resulted in the intracellular formation of 28 aryl-glycan products which were identified by MALDI and electrospray mass spectroscopy. The structures found map onto known O-glycosylation biosynthetic pathways and showed a differential pattern for each of the inhibitors in both cell lines. Gene array analysis of the glycogenes illustrated a pattern of glycosytransferases that matched the glycan structures found in glycoproteins and aryl-glycans formed in the PC/AA/C1/SB10C cells, however there was no action of the three inhibitors on glycogene transcript levels. The inhibitors act at both intermediary metabolic and genomic levels, resulting in altered protein glycosylation and arylglycan formation. These events may play a part in growth arrest. Experiment Overall Design: The effects of the O-glycan inhibitors Benzyl 2-azido-2-deoxy-alpha-D-galactopyranoside (alpha-OBn GalN3), Benzyl 2-acetamido-2-deoxy-alpha-D-galactopyranoside (alpha-OBn GalNAc), and 2-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-1-phenylethane (alpha-CBn GalNAc) on the colorectal cancer cell line PC/AA/C1/SB10C were examined. Experiment Overall Design: The PC/AA/C1/SB10C cells were treated with with 0.5 mM of the inhibitors for four days. In control experiments cells were cultivated without inhibitor. All experiments were performed twice. Total RNA was extracted with RNAzol reagent in accordance to the manufacturer instructions (PeQLab, Biotechnology Fareham, UK), treated with RNase-free DNase (DNA-free, Ambion,Warrington, UK) and integrity verified using the Agilent Bioanalyzer (Agilent Technologies, West Lothian, UK), by the presence of the 28S and 18S rRNA on agarose gels and an A260/280 ratio in the range of 1.9â2.1. A sample (5 Î¼g) of total RNA was used for production of biotinylated cRNA as described in the Affymetrix GeneChip analysis instruction manual (Affymetrix UK, High Wycombe, UK). The human genome 133A 2.0 array was then hybridized with the biotin-labeled cRNA fragments for 16 h at 45Â°C. Washing steps for the chip, staining with streptavidin-phycoerythrin, signal amplification and scanning were performed according to the manufacturerâs instructions (Affymetrix UK, High Wycombe, UK). Signal values were exported with the GeneChip operating software (GCOS, Affymetrix). Further analyses were performed with the software âCorrXpressionâ, which is described in detail elsewhere (Klein et al. 2005, J Mol Med. 83:362-376; Wessel et al. 2006, In Silico Biol.6:61-70).

Project description:Glycosylation is the most common post-translational modification of proteins, yet genes relevant to the synthesis of glycan structure and function are incompletely represented and poorly annotated on the commercially available arrays. To fill the need for expression analysis of such genes we employed the Affymetrix technology to develop a focused and highly annotated glycogene chip representing human and murine glycogenes, including glycosyltranferases, nucleotide sugar transporters, glycosidases, proteoglycans and glycan-binding proteins. In this report the array has been used to generate glycogene expression profiles of nine murine tissues. Global analysis with a hierarchical clustering algorithm, reveals that expression profiles in immune tissues (thymus, spleen, lymph node and bone marrow) are more closely related, relative to those of non-immune tissues (kidney, liver, brain and testes). Of the biosynthetic enzymes, those responsible for synthesis of the core regions of N-and O-linked oligosaccharides are ubiquitously expressed, while glycosyltransferase that elaborate terminal structures are expressed in a highly tissue-specific manner, accounting for tissue and ultimately cell type-specific glycosylation. Comparison of gene expression profiles with MALDI-TOF profiling of N-linked oligosaccharides suggested that the alpha-1-3 fucosyltransferase IX, Fut9, is the enzyme responsible for terminal fucosylation in kidney and brain, a finding validated by analysis of Fut9 knockout mice. Two families of glycan-binding proteins, C-type lectins and siglecs, are predominately expressed in the immune tissues, consistent with their emerging functions in both innate and acquired immunity. The glycogene chip reported in this study is available to the scientific community through the Consortium for Functional Glycomics (http://www.functionalglycomics.org). Keywords: Glycogenes, Glycomics, Glycosyltransferase, Lectin, Glycosylation, Glycome, Microarray, Kidney, Fut9

Dataset Information

Identification of a Novel Glycan N-linked to the Archaellins and S-layer protein of the thermophilic methanogen, Methanothermococcus thermolithotrophicus

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