Structural and Functional Characterization of New Lipid Transfer Proteins with Chitin-Binding Properties: Insights from Protein Structure Prediction, Molecular Docking, and Antifungal Activity.

Faced with the emergence of multiresistant microorganisms that affect human health, microbial agents have become a serious global threat, affecting human health and plant crops. Antimicrobial peptides have attracted significant attention in research for the development of new microbial control agents. This work's goal was the structural characterization and analysis of antifungal activity of chitin-binding peptides from Capsicum baccatum and Capsicum frutescens seeds on the growth of Candida and Fusarium species. Proteins were initially submitted to extraction in phosphate buffer pH 5.4 and subjected to chitin column chromatography. Posteriorly, two fractions were obtained for each species, Cb-F1 and Cf-F1 and Cb-F2 and Cf-F2, respectively. The Cb-F1 (C. baccatum) and Cf-F1 (C. frutescens) fractions did not bind to the chitin column. The electrophoresis results obtained after chromatography showed two major protein bands between 3.4 and 14.2 kDa for Cb-F2. For Cf-F2, three major bands were identified between 6.5 and 14.2 kDa. One band from each species was subjected to mass spectrometry, and both bands showed similarity to nonspecific lipid transfer protein. Candida albicans and Candida tropicalis had their growth inhibited by Cb-F2. Cf-F2 inhibited the development of C. albicans but did not inhibit the growth of C. tropicalis. Both fractions were unable to inhibit the growth of Fusarium species. The toxicity of the fractions was tested in vivo on Galleria mellonella larvae, and both showed a low toxicity rate at high concentrations. As a result, the fractions have enormous promise for the creation of novel antifungal compounds.

Structural characterization of a galectin from the marine sponge Aplysina lactuca (ALL) with synergistic effects when associated with antibiotics against bacteria.

Lectins presents the ability to interact with glycans and trigger varied responses, including the inhibition of the development of various pathogens. Structural studies of these proteins are essential to better understand their functions. In marine sponges, so far only a few lectins have their primary structures completely determined. Thus, the objective of this work was to structurally characterize and evaluate antibacterial potential, in association with different antibiotics, of the lectin isolated from the marine sponge Aplysina lactuta (ALL). ALL is a homotetramer of 60 kDa formed by four 15 kDa-subunits. The lectin showed affinity only for the glycoproteins fetuin, asialofetuin, mucin type III, and bovine submaxillary mucin type I. The complete amino acid sequences of two isoforms of ALL, named ALL-a and ALL-b, were determined by a combination of Edman degradation and overlapped peptides sequenced by tandem mass spectrometry. ALL-a and ALL-b have 144 amino acids with molecular masses of 15,736 Da and 15,985 Da, respectively. Both structures contain conserved residues typical of the galectin family. ALL is a protein with antibacterial potential, when in association with ampicillin and oxacillin the lectin potentiates its antibiotic effect, included Methicillin-resistant Staphylococcus strains. Thus, ALL shows to be a molecule with potential for the development of new antibacterial drugs.

Structural study and antimicrobial and wound healing effects of lectin from Solieria filiformis (Kützing) P.W.Gabrielson.

The SfL-1 isoform from the marine red algae Solieria filiformis was produced in recombinant form (rSfL-1) and showed hemagglutinating activity and inhibition similar to native SfL. The analysis of circular dichroism revealed the predominance of ß-strands structures with spectra of ßI-proteins for both lectins, which had Melting Temperature (Tm) between 41 °C and 53 °C. The three-dimensional structure of the rSfL-1 was determined by X-ray crystallography, revealing that it is composed of two ß-barrel domains formed by five antiparallel ß chains linked by a short peptide between the ß-barrels. SfL and rSfL-1 were able to agglutinate strains of Escherichia coli and Staphylococcus aureus and did not show antibacterial activity. However, SfL induced a reduction in E. coli biomass at concentrations from 250 to 125 µg mL-1, whereas rSfL-1 induced reduction in all concentrations tested. Additionally, rSfL-1 at concentrations from 250 to 62.5 µg mL-1, showed a statistically significant reduction in the number of colony-forming units, which was not noticed for SfL. Wound healing assay showed that the treatments with SfL and rSfL-1 act in reducing the inflammatory response and in the activation and proliferation of fibroblasts by a larger and fast deposition of collagen.

Trypsin/α-Amylase Inhibitors from Capsicum chinense Seeds: Characterization and Antifungal Activity against Fungi of Agronomic Importance.

BACKGROUND: Protease inhibitors (PIs) have attracted attention due to their important roles in plant defense. OBJECTIVE: The objective of this work was to characterize and evaluate the antimicrobial activity of the peptides of a family of serine PIs from Capsicum chinense Jacq. seeds. METHODS: Initially, PIs were extracted from the seeds and subjected to purification by chromatography, resulting in three different peptide enriched fractions (PEFs) termed PEF1, PEF2 and PEF3. Subsequently, the PEF3 was subjected to trypsin inhibition assays, α-amylase activity assays, antimicrobial activity assays on phytopathogenic fungi, and assays to determine the likely mechanisms of action. RESULTS: The PEF3 was composed of three protein bands with molecular masses ranging between 6 and 14 kDa. The amino acid residues of the ~6 kDa band showed high similarity with serine PIs. PEF3 inhibited the activity of the enzymes trypsin, human salivary α-amylase, and Tenebrio molitor larval α-amylase and inhibited the growth of phytopathogenic fungi, showing 83.7% loss of viability in Fusarium oxysporum. PEF3 induced reactive oxygen species in Colletotrichum lindemuthianum and F. oxysporum to dissipate their mitochondrial membrane potential and activated caspases in C. lindemuthianum. CONCLUSION: Our results reinforce the importance of PIs in plant defense mechanisms against phytopathogenic fungi as well as in their biotechnological applications for the control of plant pathogens.

Inhibition of Serine Protease, α-Amylase and Growth of Phytopathogenic Fungi by Antimicrobial Peptides from Capsicum chinense Fruits.

Plant fungal diseases cause major problems for the global economy. Antimicrobial peptides have aroused great interest in the control of phytopathogens, as they are natural molecules and have a broad spectrum of inhibitory activity. Herein, we have tried to identify and characterize antimicrobial peptides present in fruits of Capsicum chinense and to evaluate their enzymatic and antifungal activities. The retained fraction obtained in the anion exchange chromatography with strong antifungal activity was subjected to molecular exclusion chromatography and obtained four fractions named G1, G2, G3, and G4. The 6.0-kDa protein band of G2 showed similarity with protease inhibitors type II, and it was able to inhibit 100% of trypsin and α-amylase activities. The protein band with approximately 6.5 kDa of G3 showed similarity with sequences of protease inhibitors from genus Capsicum and showed growth inhibition of 48% for Colletotrichum lindemuthianum, 49% for Fusarium lateritium, and 51% for F. solani and F. oxysporum. Additionally, G3 causes morphological changes, membrane permeabilization, and ROS increase in F. oxysporum cells. The 9-kDa protein band of G4 fraction was similar to a nsLTP type 1, and a protein band of 6.5 kDa was similar to a nsLTP type 2. The G4 fraction was able to inhibit 100% of the activities of glycosidases tested and showed growth inhibition of 35 and 50% of F. oxysporum and C. lindemuthianum, respectively. C. chinense fruits have peptides with antifungal activity and enzyme inhibition with biotechnological potential.

Chia (Salvia hispanica L.) Seeds Contain a Highly Stable Trypsin Inhibitor with Potential for Bacterial Management Alone or in Drug Combination Therapy with Oxacillin.

The emergence of antibiotic resistance poses a serious and challenging threat to healthcare systems, making it imperative to discover novel therapeutic options. This work reports the isolation and characterization of a thermostable trypsin inhibitor from chia (Salvia hispanica L.) seeds, with antibacterial activity against Staphylococcus aureus sensitive and resistant to methicillin. The trypsin inhibitor ShTI was purified from chia seeds through crude extract heat treatment, followed by affinity and reversed-phase chromatography. Tricine-SDS-PAGE revealed a single glycoprotein band of ~ 11 kDa under nonreducing conditions, confirmed by mass spectrometry analysis (11.558 kDa). ShTI was remarkably stable under high temperatures (100 °C; 120 min) and a broad pH range (2-10; 30 min). Upon exposure to DTT (0.1 M; 120 min), ShTI antitrypsin activity was partially lost (~ 38%), indicating the participation of disulfide bridges in its structure. ShTI is a competitive inhibitor (Ki = 1.79 × 10-8 M; IC50 = 1.74 × 10-8 M) that forms a 1:1 stoichiometry ratio for the ShTI:trypsin complex. ShTI displayed antibacterial activity alone (MICs range from 15.83 to 19.03 µM) and in combination with oxacillin (FICI range from 0.20 to 0.33) against strains of S. aureus, including methicillin-resistant strains. Overproduction of reactive oxygen species and plasma membrane pore formation are involved in the antibacterial action mode of ShTI. Overall, ShTI represents a novel candidate for use as a therapeutic agent for the bacterial management of S. aureus infections.

A fibrinogen-related Lectin from Echinometra lucunter represents a new FReP family in Echinodermata phylum.

Fibrinogen-related proteins (FREPs) have been identified in several animals. They are involved in the body's defense, acting as mediators of phagocytosis. Ficolins and intelectins are some of the most studied Fibrinogen-related Domain (FReD)-containing lectins. In this work, we have isolated a singular FReD-containing lectin, which cannot be classified as ficolin or intelectin. ELL (Echinometra lucunter lectin) was isolated from coelomic plasma by affinity chromatography on xanthan gum. Primary structure was determined by tandem mass spectrometry. Moreover, antimicrobial activity of ELL was evaluated against planktonic cells and biofilm of Escherichia coli, Staphylococcus aureus and S. epidermidis. ELL showed hemagglutinating activity in Ca2+ presence, which was inhibited by glycoprotein mucin and thyroglobulin. Complete amino acid sequence consisted of 229 residues, including a FReD in the N-terminal. Searches for similarity found that ELL was very close to putative proteins from Strongylocentrotus purpuratus. ELL showed moderate similarity with uncharacterized sea stars proteins and protochordate intelectins. ELL was able to inhibit the planktonic growth of the Gram-positive bacteria and significantly reduce the biofilm formation of all bacteria tested. In conclusion, we identified a new type of FReP-containing lectin with some structural and functional conservation towards intelectins.

Codium isthmocladum lectin 1 (CiL-1): Interaction with N-glycans explains antinociceptive and anti-inflammatory activities in adult zebrafish (Danio rerio).

Inflammation and oxidative stress are processes associated with different human diseases. They are treated using drugs that have several side effects. Seaweed are sources of potentially relevant natural compounds for use as treatment of these disorders. Lectins are able to reversibly interact with complex carbohydrates and modulate cell membrane glycosylated receptors through this interaction. This study aimed to determine the antinociceptive and anti-inflammatory potential of CiL-1 in adult zebrafish by modulation of TRPA1 through lectin-glycan binding. Possible neuromodulation by TRPA1 channel was also evaluated by camphor pretreatment. CiL-1 was efficacious at all tested doses, revealing anti-nociceptive and anti-inflammatory effects in adult zebrafish. This galactose-binding lectin was also able to reduce the content of ROS in brain and liver. In silico analyses showed CiL-1 interactions with both ligands tested. LacNac2 presents the most favorable binding energy with the protein. The interaction occurs at 4 subsites as an extended conformation at the site. LacNac2-Sia had a less favorable curved-shape interaction energy. Based on the predictions made for the oligosaccharides, a tetra-antenate putative glycan was schematically constructed, illustrating an interaction between TRPA1 N-glycan and CiL-1. This binding seems to be related to CiL-1 anti-inflammatory activity as result of receptor modulation.

Structural characterization of a galectin isolated from the marine sponge Chondrilla caribensis with leishmanicidal potential.

BACKGROUND: Solving primary structure of lectins leads to an understanding of the physiological roles within an organism and its biotechnological potential. Only eight sponge lectins have had their primary structure fully determined. METHODS: The primary structure of CCL, Chondrilla caribensis lectin, was determined by tandem mass spectrometry. The three-dimensional structure was predicted and the protein-carbohydrate interaction analysed by molecular docking. Furthermore, the anti-leishmanial activity was observed by assays with Leishmania infantum. RESULTS: The amino acid sequence consists of 142 amino acids with a calculated molecular mass of 15,443 Da. The lectin has a galectin-like domain architecture. As observed in other sponge galectins, the signature sequence of a highly conserved domain was also identified in CCL with some modifications. CCL exhibits a typical galectin structure consisting of a ß-sandwich. Molecular docking showed that the amino acids interacting with CCL ligands at the monosaccharide binding site are mostly the same as those conserved in this family of lectins. Through its interaction with L. infantum glycans, CCL was able to inhibit the development of this parasite. CCL also induced apoptosis after eliciting ROS production and altering the membrane integrity of Leishmania infantum promastigote. CONCLUSIONS: CCL joins the restricted group of sponge lectins with determined primary structure and very high biotechnological potential owing to its promising results against pathogens that cause Leishmaniasis. GENERAL SIGNIFICANCE: As the determination of primary structure is important for biological studies, now CCL can become a sponge galectin with an exciting future in the field of human health.

H2O2 priming induces proteomic responses to defense against salt stress in maize.

KEY MESSAGE: H2O2 priming reprograms essential proteins' expression to help plants survive, promoting responsive and unresponsive proteins adjustment to salt stress. ABSTACRT: Priming is a powerful strategy to enhance abiotic stress tolerance in plants. Despite this, there is scarce information about the mechanisms induced by H2O2 priming for salt stress tolerance, particularly on proteome modulation. Improving maize cultivation in areas subjected to salinity is imperative for the local economy and food security. Thereby, this study aimed to investigate physiological changes linked with post-translational protein events induced by foliar H2O2 priming of Zea mays plants under salt stress. As expected, salt treatment promoted a considerable accumulation of Na+ ions, a 12-fold increase. It drastically affected growth parameters and relative water content, as well as promoted adverse alteration in the proteome profile, when compared to the absence of salt conditions. Conversely, H2O2 priming was beneficial via specific proteome reprogramming, which promoted better response to salinity by 16% reduction in Na+ content and shoots growth improvement, increasing 61% in dry mass. The identified proteins were associated with photosynthesis and redox homeostasis, critical metabolic pathways for helping plants survive in saline stress by the protection of chloroplasts organization and carbon fixation, as well as state redox. This research provides new proteomic data to improve understanding and forward identifying biotechnological strategies to promote salt stress tolerance.

Antihyperglycemic and antioxidant activities of a lectin from the marine red algae, Bryothamnion seaforthii, in rats with streptozotocin-induced diabetes.

The aim of the study was to assess the antihyperglycemic, antilipidemic, and antioxidant effects of a lectin isolated from Bryothamnion seaforthii (BSL), on rats with streptozotocin (STZ)-induced diabetes. The disease model was induced by low-dose injections of STZ. Diabetic rats were treated with NaCl 150 mM, metformin, and BSL at different concentrations. Blood collection was carried out at 0, 30, 60, 90, and 120 days after hyperglycemia confirmation via the assessment of seric glucose, total cholesterol, and triglycerides, assessment of the enzymatic levels of glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD), and the determination of insulin resistance by a homeostasis model of assessment-insulin resistance (HOMA-IR) as well as a homeostasis model of assessment of ß-cells resistance (HOMA-ß). The BSL-treated animals at all three concentrations showed a significant reduction in levels of glucose, cholesterol, total cholesterol, and triglycerides. Moreover, BSL increased the enzymatic activity of GPx and SOD. Index assessments of HOMA-IR and HOMA-ß confirmed that BSL treatment significantly decreased insulin resistance and ß-cell hypersecretion, respectively. In conclusion, BSL treatment might exert hypoglycemic and hypolipidemic effects, diminish insulin resistance, and ameliorate pancreatic ß-cell function along with enzymatic activities toward oxidative stress caused by diabetes mellitus type 2 (T2DM).

Proteomic identification of boar seminal plasma proteins related to sperm resistance to cooling at 17 °C.

The modern pig industry relies on extensive use of artificial insemination with cooled semen. It is important that semen doses maintain their quality during processing, transport and storage before insemination to guarantee maximum fertility rates. However, ejaculates may respond differently to liquid preservation at 17 °C, despite the optimal quality assessed before cooling. Thus, the aim of this study was to identify differences in seminal plasma proteome of ejaculates with a higher or lower seminal resistance to storage at 17 °C. A total of 148 ejaculates from 65 sexually mature healthy boars were classified as: High Resistance to cooling (HR, total motility > 60% at 144h) and Low resistance to cooling (LR, total motility <60 at 72h). To identify differentially expressed seminal plasma proteins between HR and LR ejaculates, ten ejaculates of each group were analyzed by 2D SDS-PAGE and ESI-Q-TOF mass spectrometry. The proteins associated with HR ejaculates were cathepsin B (spot 2803 and 6601, p < 0.01); spermadhesin PSP-I (spots 3101 and 3103, p < 0.05); epididymal secretory protein E1 precursor (spot 2101, p < 0.05) and IgGFc binding protein (spot 1603, p < 0.01). The protein associated with LR group was the Major seminal plasma PSPI (spot 9103, p < 0.01). To our knowledge, this is the first report of the association of boar seminal plasma proteins to semen resistance to cold storage at 17 °C. These results suggest the use of these proteins as biomarkers for semen resistance to preservation at 17 °C.

A new mucin-binding lectin from the marine sponge Aplysina fulva (AFL) exhibits antibiofilm effects.

A new mucin-binding lectin (AFL) was isolated from the marine sponge Aplysina fulva. AFL was purified by affinity chromatography on Sepharose™ matrix. Its hemagglutinating activity was independent of divalent ions, and it was weakly inhibited by simple sugars. However, porcine stomach mucin was a powerful inhibitor. In SDS PAGE, piridylethylated AFL showed one band of approximately 16 kDa, whereas in the non-reducing conditions, AFL showed at least two bands of 30 and 70 kDa. Mass spectrometry MALDI-ToF analysis showed one major ion of 31,652 ±â€¯5 Da, which corresponded to a dimer formed by subunits linked by disulfide bonds. The first fifteen amino acids of AFL were determined, and no sequence similarity was observed with any known protein. Internal sequences were obtained by mass spectrometry analysis of tryptic digestion of AFL spots. These peptides showed similarity with a lectin from marine sponge Aplysina lactuca. Secondary structure of AFL was predominantly formed by ß-conformations, which were stable at variations of pH and temperature. AFL did not inhibit planktonic growth of Gram-positive and Gram-negative bacteria tested. However, the lectin did significantly reduce the biomass biofilm of the bacteria Staphylococcus aureus, S. epidermidis, and Escherichia coli.

Proteome of the periovulatory oviduct and uterus of goats as related to nutritional balance.

This study was conducted to evaluate the effects of different feeding levels on the proteome of oviduct and uterus tissues of hormonally stimulated goats during the periovulatory period. Forty goats were separated into four different diet groups: Diet 1.0 M (n = 11), Diet 1.3 M (n = 10), Diet 1.6 M (n = 9), Diet 1.9 M (n = 10), fed with 1.0, 1.3, 1.6 and 1.9 times live weight maintenance, respectively. After four weeks of treatment, six hormonally stimulated females per treatment group were randomly selected for collection of uterine and the oviduct tissue samples. Samples were collected after animals were slaughtered in a commercial unit. Feeding goats with 1.3 to 1.9 times more nutrients than a control group directly influenced the proteome of the oviduct and uterus, altering the expression of proteins that participate in biological processes such as apoptosis, antioxidant, and immunological activities. These events are crucial for fertilization and early embryonic survival. Expression of oviduct proteins such as Tubulin Beta 2B, Transferrin and Disulphide-isomerase A3 increased in the 1.9 M group in relation to the other feeding levels. Disulphide-isomerase A4 showed higher expression in the 1.0 M group compared to diets with higher energetic levels. As energy intake increased in the diets, there was higher expression of Alpha-1-antitrypsin and downregulation of Profilin-1 in the uterus of the goats. In conclusion, this study showed that specific proteins of the goat oviduct and uterus expressed during the periovulatory period are modified as the result of nutritional balance.

Antibacterial activity of a new lectin isolated from the marine sponge Chondrilla caribensis.

A new lectin from the marine sponge Chondrilla caribensis (CCL) was isolated by affinity chromatography in Sepharose 6B media. CCL is a homotetrameric protein formed by subunits of 15,445 ±2Da. The lectin showed affinity for disaccharides containing galactose and mucin. Mass spectrometric analysis revealed about 50% of amino acid sequence of CCL, which showed similarity with a lectin isolated from Aplysina lactuca. Secondary structure consisted of 10% α-helix, 74% ß-sheet/ß-turn and 16% coil, and this profile was unaltered in a broad range of pH and temperatures. CCL agglutinated Staphylococcus aureus, S epidermidis and Escherichia coli, and it was able to reduce biofilm biomass, but showed no inhibition of planktonic growth of these bacteria. CCL activity was inhibited by α-lactose, indicating that Carbohydrate Recognition Domain (CRD) of the lectin was involved in antibiofilm activity.

Structural characterization of two isolectins from the marine red alga Solieria filiformis (Kützing) P.W. Gabrielson and their anticancer effect on MCF-7 breast cancer cells.

As described in the literature, Solieria filiformis lectin (SfL) from the marine red alga S. filiformis was found to have antinociceptive and anti-inflammatory effects. In this study, we characterized two SfL variants, SfL-1 and SfL-2, with molecular mass of 27,552Da and 27,985Da, respectively. The primary structures of SfL-1 and SfL-2 consist of four tandem-repeat protein domains with 67 amino acids each. SfL-1 and -2 showed high similarity to OAAH-family lectins. 3D structure prediction revealed that SfL-1 and -2 are composed of two ß-barrel-like domains formed by five antiparallel ß-strands, which are connected by a short peptide linker. Furthermore, the mixture of isoforms (SfLs) showed anticancer effect against MCF-7 cells. Specifically, SfLs inhibited 50% of viability in MCF-7 cells after treatment at 125µg.mL-1, while the inhibition of Human Dermal Fibroblasts (HDF) was 34% with the same treatment. Finally, 24h after treatment, 25% of MCF-7 cells were in early apoptosis and 35% in late apoptosis. Evaluation of pro- and anti-apoptotic gene expression of MCF-7 cells revealed that SfLs induced caspase-dependent apoptosis within 24h.

Isolation, biochemical characterization and antibiofilm effect of a lectin from the marine sponge Aplysina lactuca.

A new lectin was isolated from the marine sponge Aplysina lactuca (ALL) by combining ammonium sulfate precipitation and affinity chromatography on guar gum matrix. ALL showed affinity for the disaccharides α-lactose, ß-lactose and lactulose (Ka=12.5, 31.9 and 145.5M-1, respectively), as well as the glycoprotein porcine stomach mucin. Its hemagglutinating activity was stable in neutral acid pH values and temperatures below 60°C. ALL is a dimeric protein formed by two covalently linked polypeptide chains. The average molecular mass, as determined by Electrospray Ionization Mass Spectrometry (ESI-MS), was 31,810±2Da. ESI-MS data also indicated the presence of three cysteines involved in one intrachain and one interchain disulfide bond. The partial amino acid sequence of ALL was determined by tandem mass spectrometry. Eight tryptic peptides presented similarity with lectin I isolated from Axinella polypoides. Its secondary structure is predominantly ß-sheet, as indicated by circular dichroism (CD) spectroscopy. ALL agglutinated gram-positive and gram-negative bacterial cells, and it were able to significantly reduce the biomass of the bacterial biofilm tested at dose- dependent effect.

Molecular modeling, docking and dynamics simulations of the Dioclea lasiophylla Mart. Ex Benth seed lectin: An edematogenic and hypernociceptive protein.

Lectins are proteins, or glycoproteins, capable of reversibly binding to specific mono- or oligosaccharides via a noncatalytic domain. The Diocleinae subtribe presents lectins with high structural similarity, but different effects based on biological activity assays. This variability results from small structural differences. Therefore, in this context, the present study aimed to perform a structural analysis of the lectin from Dioclea lasiophylla Mart. ex Benth seeds (DlyL) and evaluate its inflammatory effect. To accomplish this, DlyL was purified in a single step by affinity chromatography on Sephadex® G-50 matrix. DlyL primary structure was determined through a combination of tandem mass spectrometry and DNA sequencing. DlyL showed high similarity with other species from the same genus. Its theoretical three-dimensional structure was predicted by homology modelling, and the protein was subjected to ligand screening with monosaccharides, oligosaccharides and complex N-glycans by molecular docking. Stability and binding of the lectin with α-methyl-d-mannoside were assessed by molecular dynamics. DlyL showed acute inflammatory response with hypernociceptive effect in the paw edema model, possibly by interaction with glycans present at the cell surface.

Purification, Biochemical Characterization, and Amino Acid Sequence of a Novel Type of Lectin from Aplysia dactylomela Eggs with Antibacterial/Antibiofilm Potential.

A new lectin from Aplysia dactylomela eggs (ADEL) was isolated by affinity chromatography on HCl-activated Sepharose™ media. Hemagglutination caused by ADEL was inhibited by several galactosides, mainly galacturonic acid (Ka = 6.05 × 106 M-1). The primary structure of ADEL consists of 217 residues, including 11 half-cystines involved in five intrachain and one interchain disulfide bond, resulting in a molecular mass of 57,228 ± 2 Da, as determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry. ADEL showed high similarity with lectins isolated from Aplysia eggs, but not with other known lectins, indicating that these lectins could be grouped into a new family of animal lectins. Three glycosylation sites were found in its polypeptide backbone. Data from peptide-N-glycosidase F digestion and MS suggest that all oligosaccharides attached to ADEL are high in mannose. The secondary structure of ADEL is predominantly ß-sheet, and its tertiary structure is sensitive to the presence of ligands, as observed by CD. A 3D structure model of ADEL was created and shows two domains connected by a short loop. Domain A is composed of a flat three-stranded and a curved five-stranded ß-sheet, while domain B presents a flat three-stranded and a curved four-stranded ß-sheet. Molecular docking revealed favorable binding energies for interactions between lectin and galacturonic acid, lactose, galactosamine, and galactose. Moreover, ADEL was able to agglutinate and inhibit biofilm formation of Staphylococcus aureus, suggesting that this lectin may be a potential alternative to conventional use of antimicrobial agents in the treatment of infections caused by Staphylococcal biofilms.

Structural studies of a vasorelaxant lectin from Dioclea reflexa Hook seeds: Crystal structure, molecular docking and dynamics.

The three-dimensional structure of Dioclea reflexa seed lectin (DrfL) was studied in detail by a combination of X-ray crystallography, molecular docking and molecular dynamics. DrfL was purified by affinity chromatography using Sephadex G-50 matrix. Its primary structure was obtained by mass spectrometry, and crystals belonging to orthorhombic space group P212121 were grown by the vapor diffusion method at 293K. The crystal structure was solved at 1.765Å and was very similar to that of other lectins from the same subtribe. The structure presented Rfactor and Rfree of 21.69% and 24.89%, respectively, with no residues in nonallowed regions of Ramachandran plot. Similar to other Diocleinae lectins, DrfL was capable of relaxing aortic rings via NO induction, with CRD participation, albeit with low intensity (32%). In silico analysis results demonstrated that DrfL could strongly interact with complex N-glycans, components of blood vessel glycoconjugates. Despite the high similarity among Diocleinae lectins, it was also reported that each lectin has unique CRD properties that influence carbohydrate binding, resulting in different biological effects presented by these molecules.