Purification and characterization of an N-acetyllactosamine-specific lectin from tubers of Arum maculatum

Lectins of the Araceae family: Insights, distinctions, and future avenues-A three-decade investigation

The Araceae family boasts >3000 species of flowering plants that thrive across the tropics. Among the focal points of study within this family are lectins, proteins with affinity for binding carbohydrates. This review endeavors to gather data gleaned from numerous studies conducted over the past three decades on lectins extracted from Araceae plants. Our examination spans their extraction and purification methods, their specific interactions with carbohydrates, their molecular structures, and various physicochemical characteristics. Furthermore, we investigated the biological activities of these lectins and investigated the outcomes of cloning their genes. Despite their apparent similarities, these lectins exhibit notable distinctions, particularly regarding their unique preferences in interacting with erythrocytes from animals and humans, their sugar affinities, the critical amino acids for their functionality, the molecular weights of their subunits and their respective topologies, and ultimately, their dimerization and 3D β-prism-II structure, which reportedly diverge from those observed in other GNA-related lectins. These discrepancies not only deepen our understanding of monocot lectins but also render these proteins inherently captivating. This review marks the inaugural attempt at consolidating almost all published reports on lectins from the Araceae family, with the aim of furnishing glycobiology scientists with essential insights into potential laboratory challenges, the characteristics of these lectins, and avenues for future research.

Purification and characterization of an asialofetuin specific lectin from the rhizome of Xanthosoma violaceum Schott

Lectins are proteins or glycoproteins that bind specifically and reversibly to the carbohydrate or glycoconjugates. A new lectin is purified from the rhizome of Xanthosoma violaceum Schott. by successive steps of ammonium sulfate fractionation and affinity chromatography with asialofetuin as ligand. The purified lectin was found to be a homotetramer of approximately 49 kDa with a subunit molecular weight of 12 kDa linked by non-covalent bonds. Characterization of the lectin shows that the hemagglutination activity is inhibited by asialofetuin and d-galacturonic acid. Hemagglutination activity is shown only in rabbit RBC but not in the human RBC of all blood groups. It is a metal ion-independent glycoprotein of 1.87% carbohydrate content, stable upto 40 °C and pH from 5.5 to 9. The lectin shows its optimum hemagglutination activity at 0 °C-40 °C and pH 6 to 8.5. From LC-MS/MS analysis it is confirmed that the purified lectin was not purified and characterized earlier.

A Useful Guide to Lectin Binding: Machine-Learning Directed Annotation of 57 Unique Lectin Specificities

Glycans are critical to every facet of biology and medicine, from viral infections to embryogenesis. Tools to study glycans are rapidly evolving; however, the majority of our knowledge is deeply dependent on binding by glycan binding proteins (e.g., lectins). The specificities of lectins, which are often naturally isolated proteins, have not been well-defined, making it difficult to leverage their full potential for glycan analysis. Herein, we use a combination of machine learning algorithms and expert annotation to define lectin specificity for this important probe set. Our analysis uses comprehensive glycan microarray analysis of commercially available lectins we obtained using version 5.0 of the Consortium for Functional Glycomics glycan microarray (CFGv5). This data set was made public in 2011. We report the creation of this data set and its use in large-scale evaluation of lectin-glycan binding behaviors. Our motif analysis was performed by integrating 68 manually defined glycan features with systematic probing of computational rules for significant binding motifs using mono- and disaccharides and linkages. Combining machine learning with manual annotation, we create a detailed interpretation of glycan-binding specificity for 57 unique lectins, categorized by their major binding motifs: mannose, complex-type N-glycan, O-glycan, fucose, sialic acid and sulfate, GlcNAc and chitin, Gal and LacNAc, and GalNAc. Our work provides fresh insights into the complex binding features of commercially available lectins in current use, providing a critical guide to these important reagents.

Purification of a mannose-binding lectin Pinellia ternata agglutinin and its induction of apoptosis in Bel-7404 cells

A novel high-throughput purification method for a monocot mannose-binding lectin, Pinellia ternata agglutinin (PTA), from tubers of P. ternata was established by mannose-Sephrose 4B affinity chromatography. The total protein was extracted from tubers of P. ternata using phosphate buffered saline (PBS) buffer. The extracted total protein was precipitated completely at 65% ammonium sulfate saturation and dissolved in different concentrations of NaCl solution to activate its binding affinity toward the column. PTA was bound to the affinity column by loading of the total protein into the column and elution using PBS buffer. The maximum purification yield (35.5mg/g) was obtained when PTA was treated with 25% (w/v) NaCl solution, and the purity of PTA analyzed by SDS-PAGE was ∼97%. The agglutination property of purified PTA was confirmed by mouse erythrocytes, which indicates its biological function. Nuclear staining assay and DNA fragmentation demonstrated that PTA could induce apoptosis of Bel-7404 cells, which further demonstrates its biological and pharmacological activities. Induction of apoptosis in the human tumor Bel-7404 cell line by PTA indicates its possible use in cancer therapy. The present investigation reports a significantly improved isolation method to obtain highly purified mannose-binding plant lectin proteins. The proposed method has great potential for industrial application because of its advantages, which include rapid isolation, high purity, high yield, low cost, and minimal requirement of chemical materials.

Phylogenetic and specificity studies of two-domain GNA-related lectins: generation of multispecificity through domain duplication and divergent evolution

A re-investigation of the occurrence and taxonomic distribution of proteins built up of protomers consisting of two tandem arrayed domains equivalent to the GNA [Galanthus nivalis (snowdrop) agglutinin] revealed that these are widespread among monotyledonous plants. Phylogenetic analysis of the available sequences indicated that these proteins do not represent a monophylogenetic group but most probably result from multiple independent domain duplication/in tandem insertion events. To corroborate the relationship between inter-domain sequence divergence and the widening of specificity range, a detailed comparative analysis was made of the sequences and specificity of a set of two-domain GNA-related lectins. Glycan microarray analyses, frontal affinity chromatography and surface plasmon resonance measurements demonstrated that the two-domain GNA-related lectins acquired a marked diversity in carbohydrate-binding specificity that strikingly contrasts the canonical exclusive specificity of their single domain counterparts towards mannose. Moreover, it appears that most two-domain GNA-related lectins interact with both high mannose and complex N-glycans and that this dual specificity relies on the simultaneous presence of at least two different independently acting binding sites. The combined phylogenetic, specificity and structural data strongly suggest that plants used domain duplication followed by divergent evolution as a mechanism to generate multispecific lectins from a single mannose-binding domain. Taking into account that the shift in specificity of some binding sites from high mannose to complex type N-glycans implies that the two-domain GNA-related lectins are primarily directed against typical animal glycans, it is tempting to speculate that plants developed two-domain GNA-related lectins for defence purposes.

Pro-inflammatory effect of Arum maculatum lectin and role of resident cells

Arum maculatum agglutinin (AMA) is a monocot lectin isolated from tubers of Arum maculatum L. (Araceae) which exhibits different specificity towards oligo-mannosidic-type and N-acetyllactosaminic-type glycans. We have investigated the effect of this lectin on the cells of the immune system. Models of neutrophil migration in vivo, neutrophil chemotaxis in vitro and macrophage cultures were used to study the lectin inflammatory activity. When administered into rat peritoneal cavities, AMA (80, 200 and 500 microg/mL/cavity) induced significant and dose-dependent neutrophil migration. This effect was inhibited by incubation with alpha-methyl-d-mannoside. A 83% depletion in the number of resident cells following peritoneal lavage did not reduce the AMA-induced neutrophil migration, as compared to sham animals (not washed). However, pre-treatment with 3% thioglycolate which increases the peritoneal macrophage population by 236%, enhanced the neutrophil migration induced by AMA (200 microg/mL/cavity) (119%, p < 0.05). Reduction of peritoneal mast cell population by chronic treatment of cavities with compound 48/80 did not modify AMA-induced neutrophil migration. The neutrophil chemotaxy assay in vitro shows that the lectin (300 microg/mL) induces neutrophil chemotaxy (368% p < 0.05) compared to RPMI. Finally, injection into peritoneal cavities of supernatants from macrophage cultures obtained after stimulation with AMA (300 microg/mL) enhanced neutrophil migration (110% p < 0.05). Summarizing, our data suggest that A. maculatum agglutinin presents pro-inflammatory activity, inducing neutrophil migration by two ways, one which is independent on resident cells and another one dependent on the presence of these cells.

Mitogenic and anti-proliferative activity of a lectin from the tubers of Voodoo lily (Sauromatum venosum)

A new lectin with the potent mitogenic and in vitro anti-proliferative activity was isolated from the tubers of a wild monocotyledonous plant Sauromatum venosum (Schott), from the family Araceae, by affinity chromatography on the asialofetuin linked amino-activated silica beads. The apparent native molecular mass of S. venosum lectin (SVL), as determined by gel filtration chromatography, was 54 kDa. In HPLC, size exclusion and cation exchange chromatography, SVL gave a single peak and also a single band of 13.5 kDa in SDS-PAGE, pH 8.3, under reducing and non-reducing conditions, indicating that the lectin is composed of four identical subunits. S. venosum lectin agglutinated rabbit, rat, sheep and guinea pig erythrocytes but reacted with goat erythrocytes after the neuraminidase treatment. However, SVL was unable to agglutinate human ABO blood group erythrocytes even after treatment with neuraminidase. SVL was inhibited by N-acetyl-D-Lactosamine (LacNAc), which is an important marker in various carcinomas and a complex desialylated glycoprotein, asialofetuin. The amino acid composition showed that lectin contained a high amount of aspartic acid and glycine but totally devoid of cysteine. However, trace amounts of methionine was present. The lectin showed a potent mitogenic response towards BALB/c splenocytes and human lymphocytes. As the mitogenic stimulation was more than that of Con A, a standard well-known plant mitogen and the response of this lectin was almost double than that of Con A. This lectin is endowed with proliferation of T cells as revealed by IL-2 bioassay but showed no production of immunoglobulins thus indicating the non-stimulation of B cells. SVL significantly inhibited the proliferation of murine cancer cell-lines, i.e., WEHI-279 to 84.6%, J774 to 81%, P388D1 to 74% and A-20 to 47%. In addition, the in vitro anti-proliferative activity of SVL was also evaluated against nine human cancer cell lines representing different organs and tissues namely, T-47D (breast), SiHa (cervix), SK-N-MC (CNS), SK-N-SH (CNS), SW-620 (colon), HT-29 (colon), HEP-2 (liver), OVCAR-5 (ovary) and PC-3 (prostate). SVL showed a significant inhibition towards the entire cell lines except the cell lines from CNS, which showed partial response in comparison to a standard anticancer drug adriamycin which was used at a concentration of 5 x 10(-5) M. Thus the anti-proliferative ability of SVL may be helpful in identification of new lectin probes that can lead to better understanding in the detection and study of certain types of cancer.

Xanthosoma sagittifolium tubers contain a lectin with two different types of carbohydrate-binding sites

An unusual lectin possessing two distinctly different types of carbohydrate-combining sites was purified from tubers of Xanthosoma sagittifolium L. by consecutive passage through two affinity columns, i.e. asialofetuin-Sepharose and invertase-Sepharose. SDS-polyacrylamide gel electrophoresis, N-terminal amino acid sequencing, and gel filtration chromatography of the purified lectin showed that the X. sagittifolium lectin is a heterotetrameric protein composed of four 12-kDa subunits (alpha(2)beta(2)) linked by noncovalent bonds. The results obtained by quantitative precipitation and hapten inhibition assays revealed that the lectin has two different types of carbohydrate-combining sites: one type for oligomannoses, which preferentially binds to a cluster of nonreducing terminal alpha1,3-linked mannosyl residues, and the other type for complex N-linked carbohydrates, which best accommodates a non-sialylated, triantennary oligosaccharide with N-acetyllactosamine (i.e. Galbeta1,4GlcNAc-) or lacto-N-biose (i.e. Galbeta1,3GlcNAc-) groups at its three nonreducing termini.