Lectins CGL and MTL, representatives of mytilectin family, exhibit different antiproliferative activity in Burkitt's lymphoma cells.

Lectins are carbohydrate-binding proteins, whose biological effects are exerted via binding to glycoconjugates expressed on the surface of cells. Exposure to lectins can lead not only to a change in the structure and properties of cells but also to their death. Here, we studied the biological activity of lectins from the mussels Crenomytilus graynus (CGL) and Mytilus trossulus (MTL) and showed that these proteins can affect the proliferation of human lymphoma cells. Both lectins suppressed the formation of colonies as well as cell cycle progression. The mechanism of action of these lectins was not mediated by reactive oxygen species but included damaging of mitochondria, inhibition of key cell cycle points, and activation of MAPK signaling pathway in tumor cells. Computer modeling suggested that various effects of CGL and MTL on lymphoma cells may be due to the difference in the energy of binding of these lectins to carbohydrate ligands on the cell surface. Thus, molecular recognition of residues of terminal carbohydrates on the surface of tumor cells is a key factor in the manifestation of the biological action of lectins.

Molecular Cloning and Characteristics of a Lectin from the Bivalve Glycymeris yessoensis.

C-type lectins (CTLs) are a family of carbohydrate-binding proteins that mediate multiple biological events, including adhesion between cells, the turnover of serum glycoproteins, and innate immune system reactions to prospective invaders. Here, we describe the cDNA cloning of lectin from the bivalve Glycymeris yessoensis (GYL), which encodes 161 amino acids and the C-type carbohydrate recognition domain (CRD) with EPN and WND motifs. The deduced amino acid sequence showed similarity to other CTLs. GYL is a glycoprotein containing two N-glycosylation sites per subunit. N-glycans are made up of xylose, mannose, D-glucosamine, 3-O-methylated galactose, D-quinovoses, and 3-O-methylated 6-deoxy-D-glucose. The potential CRD tertiary structure of the GYL adopted CTL-typical long-form double-loop structure and included three disulfide bridges at the bases of the loops. Additionally, when confirming the GYL sequence, eight isoforms of this lectin were identified. This fact indicates the presence of a multigene family of GYL-like C-type lectins in the bivalve G. yessoensis. Using the glycan microarray approach, natural carbohydrate ligands were established, and the glycotope for GYL was reconstructed as "Galß1-4GlcNAcß obligatory containing an additional fragment", like a sulfate group or a methyl group of fucose or N-acetylgalactosamine residues.

New l-Rhamnose-Binding Lectin from the Bivalve Glycymeris yessoensis: Purification, Partial Structural Characterization and Antibacterial Activity.

In this study, a new l-rhamnose-binding lectin (GYL-R) from the hemolymph of bivalve Glycymeris yessoensis was purified using affinity and ion-exchange chromatography and functionally characterized. Lectin antimicrobial activity was examined in different ways. The lectin was inhibited by saccharides possessing the same configuration of hydroxyl groups at C-2 and C-4, such as l-rhamnose, d-galactose, lactose, l-arabinose and raffinose. Using the glycan microarray approach, natural carbohydrate ligands were established for GYL-R as l-Rha and glycans containing the α-Gal residue in the terminal position. The GYL-R molecular mass determined by MALDI-TOF mass spectrometry was 30,415 Da. The hemagglutination activity of the lectin was not affected by metal ions. The lectin was stable up to 75 °C and between pH 4.0 and 12.0. The amino acid sequence of the five GYL-R segments was obtained with nano-ESI MS/MS and contained both YGR and DPC-peptide motifs which are conserved in most of the l-rhamnose-binding lectin carbohydrate recognition domains. Circular dichroism confirmed that GYL is a α/ß-protein with a predominance of the random coil. Furthermore, GYL-R was able to bind and suppress the growth of the Gram-negative bacteria E. coli by recognizing lipopolysaccharides. Together, these results suggest that GYL-R is a new member of the RBL family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity.

Spatial Structure of Lectin from the Mussel Mytilus trossulus: In-Sights from Molecular Modelling and Practical Proof.

Most proteins have the ability to self-associate into homooligomeric protein complexes, which consist of two or more identical subunits. Today, modern methods of molecular modeling are an integral part of the study of many biologically active molecules. In silico methods are widely used in structure establishing and function and activity prediction of lectins - carbohydrate-binding proteins. Here, we described by computer simulation the spatial organization of lectin isolated from the mantle of the mussel Mytilus trossulus (MTL). It was shown that the dimerization of MTL gives a total of six ligand binding sites that may be important for the manifestation its biological properties. The ability of MTL to form a dimeric and oligomeric structure was confirmed by dynamic light scattering and SDS-PAGE methods.

Activity Dependence of a Novel Lectin Family on Structure and Carbohydrate-Binding Properties.

A GalNAc/Gal-specific lectins named CGL and MTL were isolated and characterized from the edible mussels Crenomytilus grayanus and Mytilus trossulus. Amino acid sequence analysis of these lectins showed that they, together with another lectin MytiLec-1, formed a novel lectin family, adopting ß-trefoil fold. In this mini review we discuss the structure, oligomerization, and carbohydrate-binding properties of a novel lectin family. We describe also the antibacterial, antifungal, and antiproliferative activities of these lectins and report about dependence of activities on molecular properties. Summarizing, CGL, MTL, and MytiLec-1 could be involved in the immunity in mollusks and may become a basis for the elaboration of new diagnostic tools or treatments for a variety of cancers.

Structure and bioactivity of sulfated α-D-mannan from marine bacterium Halomonas halocynthiae KMM 1376T.

Halomonas halocynthiae KMM 1376T is a Gram-negative bacterium that has been isolated from gill tissue of the ascidian Halocynthia aurantium. Mild acid hydrolysis of the lipopolysaccharide of H. halocynthiae KMM 1376T afforded an O-polysaccharide, which was studied by sugar analysis and NMR spectroscopy. The following structure of the O-polysaccharide presented as sulfated α-D-mannan was established: →2)-α-D-Manp3,6S-(1→3)-α-D-Manp2Ac(∼71%)6S-(1→3)-α-D-Manp-(1→. Study of biological activity has shown that sulfated α-D-mannan can specifically reduce the cell viability and colony formation of the human breast adenocarcinoma MDA-MB-231 cells in a concentration-dependent manner. In addition, polysaccharide inhibits epidermal growth factor induced neoplastic cell transformation in mouse epidermal JB6 Cl41 cells.

Structure, antiproliferative and cancer preventive properties of sulfated α-d-fucan from the marine bacterium Vadicella arenosi.

Sulfated fucose-containing glycopolymers are currently of great interest because of their wide spectrum of bioactivity, including anti-tumor properties. In this study, the structure of O-polysaccharide (OPS) of the marine bacterium Vadicella arenosi KMM 9024T, its effect on the proliferation of human breast cancer MCF-7 cells and cancer preventive properties were investigated. Two OPS fractions with different molecular weights were isolated and purified from the lipopolysaccharide by mild acid hydrolysis followed by anion-exchange chromatography. The OPS was found to consist of α-(1→3)-linked 2-O-sulfate-d-fucopyranosyl residues, whose structure was deduced by sugar analysis along with 2D NMR spectroscopy. The biological assay indicated that polysaccharide significantly reduced the proliferation and inhibited colony formation of MCF-7 cells in a dose-dependent manner. Besides, the experiment indicated the inhibitory role of polysaccharide on EGF-induced neoplastic cell transformation in mouse epidermal cells. The investigated polysaccharide is the first sulfated fucan isolated from the bacteria.