Purification, characterization and molecular cloning of a monocot mannose-binding lectin from Remusatia vivipara with nematicidal activity

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 Comprehensive Review on Euphorbiaceae lectins: Structural and Biological Perspectives

Euphorbiaceae, also known as the spurge family, is a large group of flowering plants. Despite being tropical natives, they are now widespread. Due to its medicinal and commercial importance, this family of plants attracted a lot of attention in the scientific community. The distinctive characteristic of the family is production of milky latex, which is a rich source of several lectins, the proteins that bind carbohydrates. Although their function is unclear, they are believed to defend plants against damaging phytopathogenic microorganisms, insects, and predatory animals. Additionally, they serve as crucial metabolic regulators under a variety of stressors. Detection, separation, purification, and characterization of lectins from the Euphorbiaceae family - mostly from the latex of plants - began over 40 years ago. This effort produced over 35 original research papers that were published. However, no systematic review that compiles these published data has been presented yet. This review summarizes and describes several procedures and protocols employed for extraction and purification of lectins belonging to this family. Physicochemical properties and biological activities of the lectins, along with their medicinal and pharmacological properties, have also been analyzed. Additionally, using examples of ricin and ricin agglutinin, we have structurally analyzed characteristics of the lectin known as Ribosome Inactivating Protein Type II (RIP-Type II) that belongs to this family. We anticipate that this review article will offer a useful compendium of information on this important family of lectins, show the scientists involved in lectin research the gaps in our knowledge, and offer insights for future research.

Investigations on the Biological Activity of Allium sativum Agglutinin (ASA) Isolated from Garlic

Background:

Garlic (Allium sativum) from the family Amaryllidaceae is widely used in culinary and is reported to have potential anticancer, anti-diabetic, antimicrobial, and cardioprotective activities. Allium sativum agglutinin (ASA) is a bulb-type lectin (BTL) domaincontaining lectin isolated from garlic and has been studied for its various biological functions. Previous studies have reported the anti-cancer effects of ASA on histiocytic lymphoma (U937), promyelocytic leukemia (HL60), and oral cancer (KB).

Methods:

In this study, we have purified and characterized ASA and evaluated it for its anticancer effects on other cancer cell lines. MTT assay and FACS analysis was done to corroborate the anticancer findings against cervical (HeLa) and lung cancer (A549) cell lines.

Results:

IC50 value of 37 μg/ml in HeLa and a weak activity (26.4 ± 1.9% cellular inhibition at 100μg/ml treatment) in A549 were found in the MTT assay. FACS analysis further corroborated these findings and showed the apoptotic effects of ASA in these cell lines.

Conclusion:

Anticancer activity for members of bulb-type lectin (BTL) domain-containing lectins has been widely reported, and we hope that our study forms a basis for the development of ASA as a therapeutic agent.

Plant-Derived Lectins as Potential Cancer Therapeutics and Diagnostic Tools

Cancer remains a global health challenge, with high morbidity and mortality, despite the recent advances in diagnosis and treatment. Multiple compounds assessed as novel potential anticancer drugs derive from natural sources, including microorganisms, plants, and animals. Lectins, a group of highly diverse proteins of nonimmune origin with carbohydrate-binding abilities, have been detected in virtually all kingdoms of life. These proteins can interact with free and/or cell surface oligosaccharides and might differentially bind cancer cells, since malignant transformation is tightly associated with altered cell surface glycans. Therefore, lectins could represent a valuable tool for cancer diagnosis and be developed as anticancer therapeutics. Indeed, several plant lectins exert cytotoxic effects mainly by inducing apoptotic and autophagic pathways in malignant cells. This review summarizes the current knowledge regarding the basis for the use of lectins in cancer diagnosis and therapy, providing a few examples of plant-derived carbohydrate-binding proteins with demonstrated antitumor effects.

High mannose N-glycan binding lectin from Remusatia vivipara (RVL) limits cell growth, motility and invasiveness of human breast cancer cells

Breast cancer known for its high metastatic potential is responsible for large mortality rate amongst women; hence it is imperative to search for effective anti-metastatic molecules despite anticancer drugs. The current study describes the potential of Remusatia vivipara lectin (RVL), inducing apoptosis in breast cancer cells there by limiting motility and invasiveness. RVL binds to the cell surface glycans of MDA-MB-468 and MCF-7 cells, exhibiting strong glycan mediated cytotoxic effect, but show marginal effect on non-tumorigenic MCF-10A cells. RVL elicits increased cellular stress, apoptotic vacuoles and nuclear disintegration in both MDA-MB-468 and MCF-7 cells accompanied by depletion of G0/G1, S and G2/M phases. Lectin interaction induced production of reactive oxygen species through altering mitochondrial membrane potential progressing to apoptosis. Further, RVL strongly elicited reproductive cell death in MDA-MB-468 cells and showed strong inhibitory effect on neovascularization demonstrated in chorioallantoic membrane assay. Treatment of MDA-MB-468 cells with RVL, suppress the motility and invasive property as shown by scratch wound heal and Boyden chamber transwell assays respectively. These results provide an insight into significance of interaction of RVL with specific cell surface high mannose N-glycans resulting in curtailing the metastatic ability of cancer cells.

Purification, characterization and biological significance of mannose binding lectin from Dioscorea bulbifera bulbils

Dioscorea bulbifera or air potato has been used as a folk remedy to treat cancer. A mannose binding lectin from bulbils of D. bulbifera was purified in a single step by affinity chromatography on mucin coupled Sepharose 4B column, determined by its fine sugar specificity by glycan array analysis and studied for its clinical potential in cancer and HIV research. SDS-PAGE showed that lectin is a monomer of M_r 24kDa. DBL agglutinated only rabbit erythrocytes and was inhibited by mucin, asialomucin, fetuin, asialofetuin and transferrin but not by any monosaccharides. Glycan array analysis of DBL revealed its affinity toward high mannose N-linked glycans with enhanced affinity for terminal mannose including N-linked glycans of HIV envelope glycoprotein gp120 and has strong anti-reverse transcriptase activity. DBL showed strong binding to non-metastatic human colon epithelial cancer HT 29, metastatic SW 620 and hepatocellular HepG2 cell lines. DBL showed dose and time dependent growth inhibitory effects on all the three cell lines HT 29, SW 620 and HepG2 with IC₅₀ of 110μg, 9.8μg, 40μg respectively at 72h. Inhibitory effect of DBL was effectively blocked in presence of competing glycans like mucin. DBL has promising clinical potential both in cancer and HIV research.

Immunological characterization and expression of lily-type lectin in response to environmental stress in turbot (Scophthalmus maximus)

Lectins are a superfamily of carbohydrate-binding proteins that are widely distributed throughout living organisms. In earlier work, we identified lily-type lectin (SmLTL) in the skin mucus of turbot Scophthalmus maximus, and we characterized the protein in the present study. Results from qRT-PCR indicated that SmLTL was expressed highly in skin, intestine and gill tissue. Changes in SmLTL expression occurred in these tissues in response to environmental stressors including ciliate infection, high temperature and salinity. Recombinant SmLTL purified from Escherichia coli was able to haemagglutinate mouse erythrocytes in the absence of calcium, and was inhibited by d-mannose. In addition, SmLTL displayed selective binding to bacterial species including Edwardsiella tarda and Vibrio anguillarum, and exhibited toxicity towards Philasterides dicentrarchi, with a mortality of over 60% after 24 h at a concentration of only 100 μgml^-1. To investigate this toxicity further, we measured binding of SmLTL after incubating the ciliate in FITC-SmLTL solution. Surface fluorescence decreased substantially in the presence of 400 mM d-mannose. Together these results suggest that lily-type lectins serve as the first line of defence against microbial attack and play a pivotal role in the mucosal immune system.

High-resolution crystal structures of Colocasia esculenta tarin lectin

Tarin, the Colocasia esculenta lectin from the superfamily of α-d-mannose-specific plant bulb lectins, is a tetramer of 47 kDa composed of two heterodimers. Each heterodimer possesses homologous monomers of ~11.9 (A chain) and ~12.7 (B chain) kDa. The structures of apo and carbohydrate-bound tarin were solved to 1.7 Å and 1.91 Å, respectively. Each tarin monomer forms a canonical β-prism II fold, common to all members of Galanthus nivalis agglutinin (GNA) family, which is partially stabilized by a disulfide bond and a conserved hydrophobic core. The heterodimer is formed through domain swapping involving the C-terminal β-strand and the β-sheet on face I of the prism. The tetramer is assembled through the dimerization of the B chains from heterodimers involving face II of each prism. The 1.91 Å crystal structure of tarin bound to Manα(1,3)Manα(1,6)Man reveals an expanded carbohydrate-binding sequence (QxDxNxVxYx_4/6WX) on face III of the β-prism. Both monomers possess a similar fold, except for the length of the loop, which begins after the conserved tyrosine and creates the binding pocket for the α(1,6)-terminal mannose. This loop differs in size and amino-acid composition from 10 other β-prism II domain proteins, and may confer carbohydrate-binding specificity among members of the GNA-related lectin family.

Structural analysis and binding properties of isoforms of tarin, the GNA-related lectin from Colocasia esculenta

The lectins, a class of proteins that occur widely in animals, plants, fungi, lichens and microorganisms, are known for their ability to specifically bind to carbohydrates. Plant lectins can be classified into 12 families including the Galanthus nivalis agglutinin (GNA)-related lectin superfamily, which is widespread among monocotyledonous plants and binds specifically to mannose, a behavior that confers remarkable anti-tumor, anti-viral and insecticidal properties on these proteins. The present study characterized a mitogenic lectin from this family, called tarin, which was purified from the crude extract from taro (Colocasia esculenta). The results showed that tarin is a glycoprotein with 2-3% carbohydrate content, composed of least 10 isoforms with pIs ranging from 5.5 to 9.5. The intact protein is a heterotetramer of 47kDa composed of two non-identical and non-covalently associated polypeptides, with small subunits of 11.9kDa and large subunits of 12.6kDa. The tarin structure is stable and recovers or maintains its functional structure following treatments at different temperatures and pH. Tarin showed a complex carbohydrate specificity, binding with high affinity to high-mannose and complex N-glycans. Many of these ligands can be found in viruses, tumor cells and insects, as well as in hematopoietic progenitor cells. Chemical modifications confirmed that both conserved and non-conserved amino acids participate in this interaction. This study determined the structural and ligand binding characteristics of a GNA-related lectin that can be exploited for several different purposes, particularly as a proliferative therapeutic molecule that is able to enhance the immunological response.

Purification and characterization of the lectin from taro (Colocasia esculenta) and its effect on mouse splenocyte proliferation in vitro and in vivo

Lectins are proteins found in a wide range of organisms, with the ability to bind reversibly to specific carbohydrates. They can display important biological activities, such as the activation of the cell cycle in lymphocytes. Storage proteins with lectin activity have been reported in tuberous plant species, such as Colocasia esculenta, popularly known as taro. A simple strategy based on Cibacron Blue chromatography was used to purify a 12 kDa polypeptide 1.3-fold, with a recovery of 30 %. The purified protein was identified as tarin by mass spectrometry, which indicated that it was present in G1a/G1d isoforms. Tarin exhibited both agglutinating activity against hamster erythrocytes and mitogenic activity in vitro and in vivo toward mouse splenocytes. Optimum cellular proliferation in vitro was achieved by 625 ng of the crude extract or 500 ng of the purified tarin. Total mouse splenocyte proliferation measured after 5 days of intraperitoneal inoculation of purified tarin was increased 3.3-fold in comparison to the control group. Half of the proliferating cells were identified as B lymphocytes by flow cytometry. These results show that this is an efficient and simple strategy to purify tarin and aid in establishing this protein as a new therapeutic drug, able to promote cell proliferation in a murine model.

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.

Purification and characterization of a glucosamine-binding antifungal lectin from Phaseolus vulgaris cv. Chinese pinto beans with antiproliferative activity towards nasopharyngeal carcinoma cells

A lectin has successfully been isolated from Phaseolus vulgaris cv. Chinese pinto bean using affinity chromatography, ion exchange chromatography, and gel filtration in succession, with a 15.4-fold purification. Investigation of its characteristics revealed that Chinese pinto bean lectin (CPBL) was a 58-kDa dimeric glucosamine-binding protein. Its Mg(2+)-dependent hemagglutinating activity was stable at pH 7-8 and at or below 60 °C. When the purified lectin was tested against six fungal species including Phyllosticta citriasiana, Magnaporthe grisea, Bipolans maydis, Valsa mali, Mycosphaerella arachidicola, and Setosphaeria turcica, only the mycelial growth of V. mali was reduced by 30.6 % by the lectin at 30 μM. The lectin did not exert any discernible antiproliferative effects on breast cancer MCF-7 cells, but was able to suppress proliferation of nasopharyngeal carcinoma HONE-1 cells, with an IC50 of 17.3 μM, as revealed by the MTT assay. Since few plant lectins demonstrate antifungal activity against V. mali, and not many others have inhibitory effects on HONE-1 cells, CPBL is a distinctive lectin which may be exploited for development into an agent against V. mali and HONE-1 cells.

Prokaryotic expression and bioactivity analysis of N-terminus domain of Pinellia ternata agglutinin using alkaline phosphatase signal peptide

Pinellia ternata agglutinin (PTA) from the tubers of P. ternata is a two-domain monocot mannose-binding lectin. Pta-n encoding N-terminus domain of PTA (PTA-N) was fused with Escherichia coli alkaline phosphatase signal peptide (APSP) gene by polymerase chain reaction (PCR) for secretion expression. The fused nucleotide sequence apsp-pta-n was inserted into pET-28a prokaryotic expression vector by restriction enzyme digest sites (Nco I and Xho I), and then overexpressed in E. coli BL21(DE3) cells by isopropyl β-d-1-thiogalactopyranoside (IPTG) induction. Expressed APSP targeted the recombinant protein APSP-PTA-N into the periplasmic space, and then APSP was recognized and automatically cleaved by the membrane-bound signal peptidase. Ni-NTA chromatography was used for the purification and about 20 mg/L purified PTA-N was obtained. The minimum agglutination concentration of PTA-N determined by mice erythrocytes was 6.33 ± 0.47 μg/ml. The carbohydrate inhibition assay was carried out to determine the carbohydrate-binding property indicating PTA-N bound to specific sugars. The in vitro anti-proliferative activity towards human tumor cell lines and anti-fungal activity against Gibberella saubinetii were also demonstrated. Nuclear staining assay was performed to demonstrate PTA-N induced cell apoptosis. The results showed that PTA-N had significant biological functions, similar to native PTA. This strategy was the first time used to express plant mannose-binding lectin proteins and the product induced human tumor cell apoptosis, suggesting its potential application in biomedicine research.

Exploring the transcriptome of Atlantic salmon (Salmo salar) skin, a major defense organ

The skin of fish is the first line of defense against pathogens and parasites. The skin transcriptome of the Atlantic salmon is poorly characterized, and currently only 2,089 expressed sequence tags (ESTs) out of a total of half a million sequences are generated from skin-derived cDNA libraries. The primary aim of this study was to enhance the transcriptomic knowledge of salmon skin by using next-generation sequencing (NGS) technology, namely the Roche-454 platform. An equimolar mixture of high-quality RNA from skin and epidermal samples of salmon reared in either freshwater or seawater was used for 454-sequencing. This technique yielded over 600,000 reads, which were assembled into 34,696 isotigs using Newbler. Of these isotigs, 12 % had not been sequenced in Atlantic salmon, hence representing previously unreported salmon mRNAs that can potentially be skin-specific. Many full-length genes have been acquired, representing numerous biological processes. Mucin proteins are the main structural component of mucus and we examined in greater detail the sequences we obtained for these genes. Several isotigs exhibited homology to mammalian mucins (MUC2, MUC5AC and MUC5B). Mucin mRNAs are generally >10 kbp and contain large repetitive units, which pose a challenge towards full-length sequence discovery. To date, we have not unearthed any full-length salmon mucin genes with this dataset, but have both N- and C-terminal regions of a mucin type 5. This highlights the fact that, while NGS is indeed a formidable tool for sequence data mining of non-model species, it must be complemented with additional experimental and bioinformatic work to characterize some mRNA sequences with complex features.

Characterization and cloning of GNA-like lectin from the mushroom Marasmius oreades

A new mannose-recognizing lectin (MOL) was purified on an asialofetuin-column from fruiting bodies of Marasmius oreades grown in Japan. The lectin (MOA) from the fruiting bodies of the same fungi is well known to be a ribosome-inactivating type lectin that recognizes blood-group B sugar. However, in our preliminary investigation, MOA was not found in Japanese fruiting bodies of M. oreades, and instead, MOL was isolated. Gel filtration showed MOL is a homodimer noncovalently associated with two subunits of 13 kDa. The N-terminal sequence of MOL was blocked. The sequence of MOL was determined by cloning from cDNA and by protein sequencing of enzyme-digested peptides. The sequence shows mannose-binding motifs of bulb-type mannose-binding lectins from plants, and similarity to the sequences. Analyses of sugar-binding specificity by hemagglutination inhibition revealed the preference of MOL toward mannose and thyroglobulin, but asialofetuin was the strongest inhibitor of glycoproteins tested. Furthermore, glycan-array analysis showed that the specificity pattern of MOL was different from those of typical mannose-specific lectins. MOL preferred complex-type N-glycans rather than high-mannose N-glycans.

Pinellia ternata agglutinin expression in chloroplasts confers broad spectrum resistance against aphid, whitefly, Lepidopteran insects, bacterial and viral pathogens

Broad spectrum protection against different insects and pathogens requires multigene engineering. However, such broad spectrum protection against biotic stress is provided by a single protein in some medicinal plants. Therefore, tobacco chloroplasts were transformed with the agglutinin gene from Pinellia ternata (pta), a widely cultivated Chinese medicinal herb. Pinellia ternata agglutinin (PTA) was expressed up to 9.2% of total soluble protein in mature leaves. Purified PTA showed similar hemagglutination activity as snowdrop lectin. Artificial diet with purified PTA from transplastomic plants showed marked and broad insecticidal activity. In planta bioassays conducted with T0 or T1 generation PTA lines showed that the growth of aphid Myzus persicae (Sulzer) was reduced by 89%-92% when compared with untransformed (UT) plants. Similarly, the larval survival and total population of whitefly (Bemisia tabaci) on transplastomic lines were reduced by 91%-93% when compared with UT plants. This is indeed the first report of lectin controlling whitefly infestation. When transplastomic PTA leaves were fed to corn earworm (Helicoverpa zea), tobacco budworm (Heliothis virescens) or the beet armyworm (spodoptera exigua), 100% mortality was observed against all these three insects. In planta bioassays revealed Erwinia population to be 10,000-fold higher in control than in PTA lines. Similar results were observed with tobacco mosaic virus (TMV) challenge. Therefore, broad spectrum resistance to homopteran (sap-sucking), Lepidopteran insects as well as anti-bacterial or anti-viral activity observed in PTA lines provides a new option to engineer protection against biotic stress by hyper-expression of an unique protein that is naturally present in a medicinal plant.

Purification, characterization, and molecular cloning of lectin from winter buds of Lysichiton camtschatcensis (L.) Schott

A novel lectin was purified to homogeneity from winter buds of Lysichiton camtschatcensis (L.) Schott of the Araceae family. It was a tetramer composed of two non-covalently associated polypeptides with small subunits (11 kDa) and large subunits (12 kDa). Sequencing of both subunits yielded unique N-terminal sequences. A cDNA encoding the lectin was cloned. The isolated cDNA contained an open reading frame that encoded 267 amino acids. It encoded both subunits, indicating that the lectin is synthesized as a single precursor protein that is post-translationally processed into two different subunits with 45% sequence identity. Each subunit contained a mannose-binding motif known to be conserved in monocot mannose-binding lectins, but its activity was not inhibited by monosaccharides, including methyl α-mannoside. Asialofetuin and yeast invertase were potent inhibitors. Lectin activity was detected in the buds formed during the winter season but not in the expanded leaves.

Crystal structure of a β-prism II lectin from Remusatia vivipara

The crystal structure of a β-prism II (BP2) fold lectin from Remusatia vivipara, a plant of traditional medicinal value, has been determined at a resolution of 2.4 Å. This lectin (RVL, Remusatia vivipara lectin) is a dimer with each protomer having two distinct BP2 domains without a linker between them. It belongs to the "monocot mannose-binding" lectin family, which consists of proteins of high sequence and structural similarity. Though the overall tertiary structure is similar to that of lectins from snowdrop bulbs and garlic, crucial differences in the mannose-binding regions and oligomerization were observed. Unlike most of the other structurally known proteins in this family, only one of the three carbohydrate recognition sites (CRSs) per BP2 domain is found to be conserved. RVL does not recognize simple mannose moieties. RVL binds to only N-linked complex glycans like those present on the gp120 envelope glycoprotein of HIV and mannosylated blood proteins like fetuin, but not to simple mannose moieties. The molecular basis for these features and their possible functional implications to understand the different levels of carbohydrate affinities in this structural family have been investigated through structure analysis, modeling and binding studies. Apart from being the first structure of a lectin to be reported from the Araceae/Arum family, this protein also displays a novel mode of oligomerization among BP2 lectins.

Lectins: production and practical applications

Lectins are proteins found in a diversity of organisms. They possess the ability to agglutinate erythrocytes with known carbohydrate specificity since they have at least one non-catalytic domain that binds reversibly to specific monosaccharides or oligosaccharides. This articles aims to review the production and practical applications of lectins. Lectins are isolated from their natural sources by chromatographic procedures or produced by recombinant DNA technology. The yields of animal lectins are usually low compared with the yields of plant lectins such as legume lectins. Lectins manifest a diversity of activities including antitumor, immunomodulatory, antifungal, HIV-1 reverse transcriptase inhibitory, and anti-insect activities, which may find practical applications. A small number of lectins demonstrate antibacterial and anti-nematode activities.