Plant Lectin

Phoenix dactylifera (date palm) holds significant medicinal value, particularly in traditional medicine. This study focuses on purifying and characterizing a lectin (PdSL) extracted from its seeds and assessing its physicochemical stability, glycoprotein nature, and therapeutic properties,
including analgesic and gastroprotective activities. PdSL was extracted via phosphate-buffered saline (PBS) and purified via ion exchange and affinity chromatography, resulting in a twofold increase in purity. Stability tests included varying temperatures (40–100°C), pH levels (2–13), and
exposure to denaturing agents. Biological assays were used to evaluate its analgesic effects in thermal (hot plate, p < 0.05) and chemical (acetic acid writhing, p < 0.01) pain models.
Gastroprotective activity was assessed in an ethanol-induced gastric ulcer model in rats, with statistical significance at P < 0.05. PdSL demonstrated exceptional stability, retaining activity across a broad range of temperatures (up to 100°C) and pH values (5.5–9.5). The lectin maintained hemagglutination activity under challenging conditions and showed specificity for sheep erythrocytes and mannose-binding properties. It was identified as a glycoprotein with 37.64% neutral sugars and exhibited a hydrophobic binding site for adenine. In analgesic assays, PdSL significantly increased the pain threshold in the hotplate test, particularly at 6 mg/kg after 60 minutes (p < 0.003), and in the writhing test, with a dose-dependent pain inhibition of 80–89% (p < 0.01). Gastroprotective activity revealed dose-dependent ulcer inhibition, with a maximum reduction of 89% at 1 mg/kg (p < 0.0001), along with normalization of the gastric pH. PdSL from Phoenix dactylifera seeds exhibits remarkable stability and therapeutic efficacy, including painrelieving and antiulcer activities, with statistically significant results highlighting its potential as a candidate for drug development. These findings encourage further exploration of plant-derived lectins in biomedical research.

Lectins are defined as the carbohydrate-binding proteins of non-immune origin that can interact and precipitates glycoconjugates from their solutions. Due to these features, many applications have been discovered for these proteins. The present investigation has been devoted to optimising a protocol for the extraction, purification and characterization of a lectin from the seeds of the medicinal plant Ocimum basilicum (OBSL). Different extraction procedures were employed, including varying buffers with variable pHs. Precipitation of the seeds' crude protein extract with salting-out using solid ammonium sulphate (AmS) at 40, 60 and 80% concentrations resulted in the segregation of the lectins into at least three isoforms. The lectin was purified to apparent electrophoretic homogeneity by fetuin-agarose affinity resin. The lectin was a trimer composed of three subunits of different molecular weights. Scanning the three AmS precipitated protein fractions at the UV ranges, indicates that the protein is rich in tryptophan rather than tyrosine. The lectin haemagglutination pattern studies showed that OBSL had a better affinity for the B+ human blood group, sheep and rabbit erythrocytes as compared to other human and animal blood types. The lectin was not inhibited by any simple sugar indicating its classification as a lectin with complex sugar specificity. OBSL was stable within the pH range from 2.5 to 10.5 showing two pH activity optima. It was optimally active from 40 to 50 °C. This study represents the first-ever report on this plant lectin and might stimulate further studies to extensively characterize this protein.

Cancer kills almost 8 million people per year worldwide (about 13 people every minute). Clearly, current cancer treatments are not completely effective. In addition, many chemotherapeutic reagents attack rapidly dividing cells, which renders them toxic to a wide array of normal cells in addition to cancer cells. This lack of specificity can cause collateral damage and significant side effects in patients. More targeted therapies are needed to successfully combat cancer. Tumor cell motility leads to invasion and metastasis that cause the vast majority of cancer deaths. We and others have found that the podoplanin (PDPN) receptor promotes tumor cell motility that contributes to many types of cancer. PDPN has a short intracellular domain of 9 amino acids which include two conserved serine residues. PDPN also has a large extracellular domain that is extensively O-glycosylated with α2,3-sialic acid linked to galactose. We are developing reagents to target the intracellular and extracellular domains of PDPN to inhibit cancer progression. For example, we have found that some activators of protein kinase A can induce phosphorylation of the intracellular serine residues of PDPN to inhibit tumor cell motility. In addition, we have found that Maackia amurensis seed lectin (MASL) can target the extracellular domain of PDPN to inhibit transformed cell growth and motility. The biological activity of this lectin survives gastrointestinal proteolysis and enters the cardiovascular circulatory system to inhibit tumor vascularization and progression. Furthermore, we utilized live cell imaging to find that PDPN expression in cancer associated fibroblasts can promote neighboring tumor cell migration and survival. Thus, reagents can be used to target PDPN from inside of the cell and outside of the cell to inhibit tumor cell migration and combat cancer progression. This work illuminates strategies designed to exploit PDPN as a functionally relevant biomarker and chemotherapeutic target.

Selective targeting of drugs to the proposed site of action provides therapeutic advantages such as reduced toxicity and smaller dose levels. Despite a huge progress made in drug design and delivery systems, many challenges still have to be solved. Small therapeutic drugs always have the potential to pass into the kidneys and be excreted from the body. The use of macromolecular constructs (carriers) that allow longer circulation times, contribute to improved chemical functionality and more precise drug delivery is an attractive alternative option. Bioadhesive systems which will utilize intense contact to increase the drug concentration gradient could be an attractive approach. Because of their specific carbohydrate-binding, lectins can interact with glycoconjugates present on the epithelial cells that line all of the organs exposed to the external environment. The unique carbohydrate specificities of plant lectins can facilitate mucoadhesion and cytoadhesion of drugs. As immunostimulatory molecules with an adjuvant effect plant lectins can also be employed in vaccine development.

Stress granules are cytoplasmic compartments, which serve as mRNA storage units during stress, therefore regulating translation. The Arabidopsis thaliana lectin ArathEULS3 has been widely described as a stress inducible gene. This study aimed to examine in detail the localization of ArathEULS3 lectin in normal and stressed cells. Colocalization experiments revealed that the nucleo-cytoplasmic lectin ArathEULS3 relocates to stress granules after stress. The ArathEULS3 sequence encodes a protein with a EUL lectin domain and an N-terminal domain with unknown structure and function. Bioinformatics analyses showed that the N-terminal domain sequence contains intrinsically disordered regions and likely does not exhibit a stable protein fold. Plasmolysis experiments indicated that ArathEULS3 also localizes to the apoplast, suggesting that this protein might follow an unconventional route for secretion. As part of our efforts we also investigated the interactome of ArathEULS3 and identified...

Ginseng, a popular and valuable traditional medicine, has been used for centuries to maintain health and treat disease. Here we report the discovery and characterization of ginsentides, a novel family of cysteine and glycine-rich peptides derived from the three most widely-used ginseng species: Panax ginseng, Panax quinquefolius, and Panax notoginseng. Using proteomic and transcriptomic methods, we identified 14 ginsentides, TP1-TP14 which consist of 31-33 amino acids and whose expression profiles are species- and tissues-dependent. Ginsentides have an eight-cysteine motif typical of the eight-cysteine-hevein-like peptides (8C-HLP) commonly found in medicinal herbs, but lack a chitin-binding domain. Transcriptomic analysis showed that the three-domain biosynthetic precursors of ginsentides differ from known 8C-HLP precursors in architecture and the absence of a C-terminal protein-cargo domain. A database search revealed an additional 50 ginsentide-like precursors from both gymnosper...

The partial amino acid sequence of the tetrameric isolectin B4 from Vicia villosa seeds has been determined by peptide analysis, and its three-dimensional structure solved by molecular replacement techniques and refined at 2.9 A resolution to a crystallographic /J-factor of 21%. Each subunit displays the thirteen-stranded P-barrel topology characteristic of legume lectins. The amino acid residues involved in metal-and sugarbinding are similar to those of other GalNAc-specific lectins, indicating that residues outside the carbohydrate-binding pocket modulate the affinity for the Tn glycopeptide. Isolectin B4 displays an unusual quaternary structure, probably due to protein glycosylation.

The partial amino acid sequence of the tetrameric isolectin B4 from Vicia villosa seeds has been determined by peptide analysis, and its three-dimensional structure solved by molecular replacement techniques and refined at 2.9 A resolution to a crystallographic /J-factor of 21%. Each subunit displays the thirteen-stranded P-barrel topology characteristic of legume lectins. The amino acid residues involved in metal-and sugarbinding are similar to those of other GalNAc-specific lectins, indicating that residues outside the carbohydrate-binding pocket modulate the affinity for the Tn glycopeptide. Isolectin B4 displays an unusual quaternary structure, probably due to protein glycosylation.

The anti-nociceptive and anti-inflammatory activity of the lectin purified from Tetracarpid-ium conophorum seeds were investigated. The lectin was purified from the phosphate buffered saline crude extract of the seeds using gel filtration and affinity chromatography techniques. Hemagglutination assay and hapten-sugar inhibition test were carried out to ascertain the blood group and sugar specificities of the lectin respectively. Anti-nociceptive and anti-inflammatory activities of the lectin were evaluated (in-vivo) with standard models including formalin licking test, carrageenan-induced paw edema test and peritonitis model. A yield, purification fold and subunit molecular weight of 27%, 17 and 34 kDa respectively were obtained for the purified lectin from T. conophorum seed (TcSL). The lac-tose/galactose specific TcSL showed significant inhibition (p < 0.05) of nociception as measured by paw licking time upon pain induction by formalin and inflammation as measured by paw swollenness induced by sub-plantar injection of carrageenan. The lectin also significantly reduced carrageenan-induced leucocyte migration to the peritoneum in a dose-dependent manner. The study concluded that TcSL showed anti-nociceptive and anti-inflammatory activities and thus poised to be a good bio-active peptide for the design of novel anti-inflammatory therapy.