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

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.

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.

Man-Specific Lectins from Plants, Fungi, Algae and Cyanobacteria, as Potential Blockers for SARS-CoV, MERS-CoV and SARS-CoV-2 (COVID-19) Coronaviruses: Biomedical Perspectives

Betacoronaviruses, responsible for the “Severe Acute Respiratory Syndrome” (SARS) and the “Middle East Respiratory Syndrome” (MERS), use the spikes protruding from the virion envelope to attach and subsequently infect the host cells. The coronavirus spike (S) proteins contain receptor binding domains (RBD), allowing the specific recognition of either the dipeptidyl peptidase CD23 (MERS-CoV) or the angiotensin-converting enzyme ACE2 (SARS-Cov, SARS-CoV-2) host cell receptors. The heavily glycosylated S protein includes both complex and high-mannose type N-glycans that are well exposed at the surface of the spikes. A detailed analysis of the carbohydrate-binding specificity of mannose-binding lectins from plants, algae, fungi, and bacteria, revealed that, depending on their origin, they preferentially recognize either complex type N-glycans, or high-mannose type N-glycans. Since both complex and high-mannose glycans substantially decorate the S proteins, mannose-specific lectins are potentially useful glycan probes for targeting the SARS-CoV, MERS-CoV, and SARS-CoV-2 virions. Mannose-binding legume lectins, like pea lectin, and monocot mannose-binding lectins, like snowdrop lectin or the algal lectin griffithsin, which specifically recognize complex N-glycans and high-mannose glycans, respectively, are particularly adapted for targeting coronaviruses. The biomedical prospects of targeting coronaviruses with mannose-specific lectins are wide-ranging including detection, immobilization, prevention, and control of coronavirus infection.

Exploration of carbohydrate binding behavior and anti-proliferative activities of Arisaema tortuosum lectin

BACKGROUND

Lectins have come a long way from being identified as proteins that agglutinate cells to promising therapeutic agents in modern medicine. Through their specific binding property, they have proven to be anti-cancer, anti-insect, anti-viral agents without affecting the non-target cells. The Arisaema tortuosum lectin (ATL) is a known anti-insect and anti-cancer candidate, also has interesting physical properties. In the present work, its carbohydrate binding behavior is investigated in detail, along with its anti-proliferative property.

RESULTS

The microcalorimetry of ATL with a complex glycoprotein asialofetuin demonstrated trivalency contributed by multiple binding sites and enthalpically driven spontaneous association. The complex sugar specificity of ATL towards multiple sugars was also demonstrated in glycan array analysis in which the trimannosyl pentasaccharide core N-glycan [Manα1-6(Manα1-3)Manβ1-4GlcNAcβ1-4GlcNAcβ] was the highest binding motif. The high binding glycans for ATL were high mannans, complex N-glycans, core fucosylated N-glycans and glycans with terminal lactosamine units attached to pentasaccharide core. ATL induced cell death in IMR-32 cells was observed as time dependent loss in cell number, formation of apoptotic bodies and DNA damage. As a first report of molecular cloning of ATL, the in silico analysis of its cDNA revealed ATL to be a β-sheet rich heterotetramer. A homology model of ATL showed beta prism architecture in each monomer with 85% residues in favoured region of Ramachandran plot.

CONCLUSIONS

Detailed exploration of carbohydrate binding behavior indicated ATL specificity towards complex glycans, while no binding to simple sugars, including mannose. Sequence analysis of ATL cDNA revealed that during the tandem evolutionary events, domain duplication and mutations lead to the loss of mannose specificity, acquiring of new sugar specificity towards complex sugars. It also resulted in the formation of a two-domain single chain polypeptide with both domains having different binding sites due to mutations within the consensus carbohydrate recognition sites [QXDXNXVXY]. This unique sugar specificity can account for its significant biological properties. Overall finding of present work signifies anti-cancer, anti-insect and anti-viral potential of ATL making it an interesting molecule for future research and/or theragnostic applications.

Overview of the Structure⁻Function Relationships of Mannose-Specific Lectins from Plants, Algae and Fungi

To date, a number of mannose-binding lectins have been isolated and characterized from plants and fungi. These proteins are composed of different structural scaffold structures which harbor a single or multiple carbohydrate-binding sites involved in the specific recognition of mannose-containing glycans. Generally, the mannose-binding site consists of a small, central, carbohydrate-binding pocket responsible for the "broad sugar-binding specificity" toward a single mannose molecule, surrounded by a more extended binding area responsible for the specific recognition of larger mannose-containing N-glycan chains. Accordingly, the mannose-binding specificity of the so-called mannose-binding lectins towards complex mannose-containing N-glycans depends largely on the topography of their mannose-binding site(s). This structure⁻function relationship introduces a high degree of specificity in the apparently homogeneous group of mannose-binding lectins, with respect to the specific recognition of high-mannose and complex N-glycans. Because of the high specificity towards mannose these lectins are valuable tools for deciphering and characterizing the complex mannose-containing glycans that decorate both normal and transformed cells, e.g., the altered high-mannose N-glycans that often occur at the surface of various cancer cells.