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- Olausson, Johan, 1980-, et al.
(författare)
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Production and characterization of a monomeric form and a single-site form of Aleuria aurantia lectin
- 2011
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Ingår i: Glycobiology. - : Oxford University Press. - 0959-6658 .- 1460-2423. ; 21:1, s. 34-44
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Tidskriftsartikel (refereegranskat)abstract
- Lectins have been widely used in structural and functional studies of complex carbohydrates. Lectins usually bind carbohydrates with relatively low affinity but compensate for this by multivalency. When using lectins in different biological and analytical assays the multivalent nature of lectins can sometimes produce unwanted reactions such as agglutination or precipitation of target glycoproteins. The mushroom lectin Aleuria aurantia binds to fucose-containing oligosaccharides. It is composed of two identical subunits where each subunit contains five binding sites for fucose. In the present study two forms of recombinant AAL were produced using site-directed mutagenesis. A monomeric form of AAL was produced by exchange of Tyr6 to Arg6, and a monovalent fragment of AAL was produced by insertion of a NdeI restriction enzyme cleavage site and a stop codon in the coding sequence. The AAL forms were expressed as His-tagged proteins in E.coli and purified by affinity chromatography. Binding properties of the two AAL forms were performed using hemagglutination assay, surface plasmon resonance and enzyme-linked lectin assay analyses. Both the monomeric AAL form (mAAL) and the monovalent AAL form (S2-AAL) retained their capacity to bind fucosylated oligosaccharides. However, both constructs exhibited properties that differed from the intact recombinant AAL (rAAL). Monomeric AAL showed similar binding affinities to fucosylated oligosaccharides compared to rAAL but had less hemagglutinating capacity. S2-AAL showed a lower binding affinity to fucosylated oligosaccharides and, in contrast to rAAL and mAAL, S2-AAL did not bind to sialylated fuco-oligosaccharides such as sialyl-Lex. The study shows that molecular engineering techniques may be a tool for producing lectins with more defined properties such as decreased valency and defined specificities and affinities. This may be very valuable for development of reliable diagnostic and biological assays for carbohydrate analysis.
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- Rydell, Gustaf E, et al.
(författare)
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Human noroviruses recognize sialyl Lewis x neoglycoprotein
- 2009
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Ingår i: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 19:3, s. 309-320
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Tidskriftsartikel (refereegranskat)abstract
- The carbohydrate binding characteristics of a norovirus GII.3 (Chron1) and a GII.4 (Dijon) strain were investigated using virus-like particles (VLPs) and saliva samples from 81 individuals genotyped for FUT2 (secretor) and FUT3 (Lewis) and phenotyped for ABO and Lewis blood groups. The two VLPs showed a typical secretor-gene-dependent binding and bound significantly stronger to saliva from A, B, and AB than from O individuals (P < 0.0001 and P < 0.001) but did not bind to any samples from secretor-negative individuals. The GII.3 strain showed larger interindividual variation and bound stronger to saliva from B than from A(2) secretors (P < 0.01). When assaying for binding to neoglycoproteins, the GII.3 and GII.4 strains were compared with the Norwalk GI.1 prototype strain. Although all three strains bound to Lewis b (and H type 1 chain) glycoconjugates, only the two GII strains showed an additional binding to sialyl Lewis x. This novel binding was specific since the VLPs did not bind to structural analogs, e.g., Lewis x or sialyl Lewis a, but only to sialyl Lewis x, sialyl diLewis x and sialylated type 2 chain conjugates. In inhibition experiments, the sialyl Lewis x conjugate was the most potent inhibitor. The minimal requirement for this potential receptor structure is Neu5Ac alpha 3Gal beta 4(Fuc alpha 3)GlcNAc beta 3Gal beta- where Fuc is not absolutely necessary for binding. Our study shows that some human norovirus GII strains have at least two binding specificities: one secretor-gene-dependent related to alpha 1,2-fucosylated carbohydrates and another related to alpha 2,3-sialylated carbohydrates of the type 2 chain, e.g., sialyl Lewis x.
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- Venkatakrishnan, Vignesh, 1987, et al.
(författare)
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Novel inhibitory effect of galectin-3 on the respiratory burst induced by Staphylococcus aureus in human neutrophils
- 2023
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Ingår i: Glycobiology. - : OXFORD UNIV PRESS INC. - 1460-2423 .- 0959-6658. ; 33:6, s. 503-511
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Tidskriftsartikel (refereegranskat)abstract
- Among the responders to microbial invasion, neutrophils represent the earliest and perhaps the most important immune cells that contribute to host defense with the primary role to kill invading microbes using a plethora of stored anti-microbial molecules. One such process is the production of reactive oxygen species (ROS) by the neutrophil enzyme complex NADPH-oxidase, which can be assembled and active either extracellularly or intracellularly in phagosomes (during phagocytosis) and/or granules (in the absence of phagocytosis). One soluble factor modulating the interplay between immune cells and microbes is galectin-3 (gal-3), a carbohydrate-binding protein that regulates a wide variety of neutrophil functions. Gal-3 has been shown to potentiate neutrophil interaction with bacteria, including Staphylococcus aureus, and is also a potent activator of the neutrophil respiratory burst, inducing large amounts of granule-localized ROS in primed cells. Herein, the role of gal-3 in regulating S. aureus phagocytosis and S. aureus-induced intracellular ROS was analyzed by imaging flow cytometry and luminol-based chemiluminescence, respectively. Although gal-3 did not interfere with S. aureus phagocytosis per se, it potently inhibited phagocytosis-induced intracellular ROS production. Using the gal-3 inhibitor GB0139 (TD139) and carbohydrate recognition domain of gal-3 (gal-3C), we found that the gal-3-induced inhibitory effect on ROS production was dependent on the carbohydrate recognition domain of the lectin. In summary, this is the first report of an inhibitory role of gal-3 in regulating phagocytosis-induced ROS production.
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