Legume lectins interact with muramic acid and N-acetylmuramic acid

Isolation and partial characterisation of a novel lectin from Aegle marmelos fruit and its effect on adherence and invasion of Shigellae to HT29 cells

Lectins are a class of ubiquitous proteins/glycoproteins that are abundantly found in nature. Lectins have unique carbohydrate binding property and hence have been exploited as drugs against various infectious diseases. We have isolated one such novel lectin from the fruit pulp of Aegle marmelos. The isolated lectin was partially characterised and its effect against Shigella dysenteriae infection was evaluated. The isolated lectin was found to be a dimeric protein with N-acetylgalactosamine, mannose and sialic acid binding specificity. The effect of Aegle marmelos fruit lectin on the adherence of Shigella dysenteriae to human colonic epithelial cells (HT29 cells) was evaluated by Enzyme Linked Immune Sorbent Assay and invasion was analysed. The protective nature of the Aegle marmelos fruit lectin was assessed by analyzing apoptosis through dual staining method. Aegle marmelos fruit lectin significantly inhibited hemagglutination activity of Shigella and its minimum inhibitory concentration is 0.625 µg/well. Further, at this concentration lectin inhibited Shigella dysenteriae adherence and invasion of HT29 cells and protects the HT29 cells from Shigella dysenteriae induced apoptosis. To conclude, isolated lectin dimeric protein with N-acetylgalactosamine, Mannose and sialic acid binding specificity and inhibits adherence and invasion of Shigellae to HT29 cells thus, protects the host.

Purification and biological effects of Araucaria angustifolia (Araucariaceae) seed lectin

This paper describes the purification and characterization of a new N-acetyl-d-glucosamine-specific lectin from Araucaria angustifolia (AaL) seeds (Araucariaceae) and its anti-inflammatory and antibacterial activities. AaL was purified using a combination of affinity chromatography on a chitin column and ion exchange chromatography on Sephacel-DEAE. The pure protein has 8.0kDa (SDS-PAGE) and specifically agglutinates rabbit erythrocytes, effect that was independent of the presence of divalent cations and was inhibited after incubation with glucose and N-acetyl-d-glucosamine. AaL showed antibacterial activity against Gram-negative and Gram-positive strains, shown by scanning electron microscopy. AaL, intravenously injected into rats, showed anti-inflammatory effect, via carbohydrate site interaction, in the models of paw edema and peritonitis. This lectin can be used as a tool for studying bacterial infections and inflammatory processes.

Breaching the great wall: peptidoglycan and microbial interactions

Once thought to be a process that occurred only in a few human pathogens, release of biologically active peptidoglycan fragments during growth by Gram-negative bacteria controls many types of bacterial interaction, including symbioses and interactions between microorganisms. This Perspective explores the role of peptidoglycan fragments in mediating a range of microbial-host interactions, and discusses the many systems in which peptidoglycan fragments released during bacterial growth might be active.

Lectins from Pisum arvense seeds behave differently from storage proteins during germination in the darkness

ABSTRACT - The mobilization of seed proteins from Pisum arvense L. during germination in the absence of light was studied. The seeds were found to be completely consumed 22 days after germination and seedlings ceased growth after the 18th day. SDS-PAGE indicated that the main protein bands correspond to high molecular mass storage proteins which undergo proteolysis in the initial stages of germination and are not detected after the 7th day of germination. However, the corresponding lectin profiles were detected during the entire germination process, suggesting that these proteins are strongly resistant to seed proteolytic enzymes and should be important for seedling establishment. Furthermore, haemagglutinating activity in cotyledons was detected until 22 days after germination, indicating that the lectins remain active even in senescent cotyledons.

The carbohydrate-binding specificity and molecular modelling of Canavalia maritima and Dioclea grandiflora lectins

The carbohydrate-binding specificity of lectins from the seeds of Canavalia maritima and Dioclea grandiflora was studied by hapten-inhibition of haemagglutination using various sugars and sugar derivatives as inhibitors, including N-acetylneuraminic acid and N-acetylmuramic acid. Despite some discrepancies, both lectins exhibited a very similar carbohydrate-binding specificity as previously reported for other lectins from Diocleinae (tribe Phaseoleae, sub-tribe Diocleinae). Accordingly, both lectins exhibited almost identical hydropathic profiles and their three-dimensional models built up from the atomic coordinates of ConA looked very similar. However, docking experiments of glucose and mannose in their monosaccharide-binding sites, by comparison with the ConA-mannose complex used as a model, revealed conformational changes in side chains of the amino acid residues involved in the binding of monosaccharides. These results fully agree with crystallographic data showing that binding of specific ligands to ConA requires conformational chances of its monosaccharide-binding site.

Binding and degradation of lectins by components of rumen liquor

The binding of 15 different plant lectins to feed particles and microbes in rumen liquor, and their degradation were studied in vitro. The rate of degradation assessed from the label released when radioactive iodine-labelled lectins were incubated with rumen liquor conflicted with the rates calculated from measurements of the survival of the antigenic structure (immuno-rocket electrophoresis) or the biological function (haemagglutination) of the lectins. Thus solubilization of the radioactive label indicated that Concanavalin A (Con A), but not the soyabean agglutinin, SBA, or kidney bean phytohaemagglutinin, PHA-E3L, was stable to rumen proteolysis. In contrast, both SBA and PHA-E3L were shown by immuno-rocket electrophoresis or haemagglutination tests to be highly resistant to breakdown, while the degradation of Con A proceeded at a constant slow rate under the same conditions. This was in accord with the previously established general stability of lectins in the gut of single-stomach animals. Of the 15 lectins, SBA, favin (Vicia faba lectin) and Con A were bound by hay and the particle fraction of rumen liquor. This was, in part, specific and reversible in the presence of appropriate sugars. Most pure bacterial strains preferentially bound lectins with specificity for glucose/mannose (favin and Con A), while rumen fungi reacted with SBA. The level of binding was low with other lectins. However, inter-strain differences of lectin-binding were found in Selenomonas ruminantium and Ruminococcus flavefaciens. Clearly, as some lectins were not fully degraded in the rumen, they could be expected to depress the utilization of the diet not only in single-stomach animals but, possibly, also in ruminants.

A dot blot technique for the analysis of interactions of lectins with glycosaminoglycans

Glycosaminoglycans are polysaccharides which are widely distributed throughout connective tissue, where they form an essential part of the extracellular matrix. Connective tissue is often stained by lectins, and it is not known whether this staining is due to the interaction of lectins with the glycosaminoglycans or due to the binding of lectins to other glycoconjugates within the matrix. A dot blot technique is presented by which the interaction of lectins with glycosaminoglycans can be analysed.

Fine sugar specificity of the Butea frondosa seed lectin

Various monosaccharides and oligosaccharides were used to define the specificity of the Butea frondosa lectin using the hapten inhibition technique of human erythrocyte agglutination. Although B. frondosa lectin exhibited higher affinity for N-acetylgalactosamine, lactose and N-acetyllactosamine appeared to be relatively good inhibitors of haemagglutination. The behaviour of N-acetyllactosamine-type oligosaccharides and glycopeptides on a column of B. frondosa lectin immobilized on Sepharose 4B showed that the sugar-binding specificity of the lectin is directed towards unmasked N-acetyllactosamine sequences. Substitution of these N-acetyllactosamine sequences by sialic acid residues completely abolished the affinity of the lectin for the saccharides. The presence of one or several alpha Fuc(1-3)GlcNAc groups completely inhibited the interaction between the glycopeptides and the lectin. Substitution of the core beta-mannose residue by an additional bisecting beta(1-4)GlcNAc residue decreases the affinity of the lectin for these structures as compared with the unsubstituted ones.