Sugar-binding Proteins Research Articles

Pseudomonas aeruginosa polysaccharide Psl supports airway microbial community development

Pseudomonas aeruginosa dominates the complex polymicrobial cystic fibrosis (CF) airway and is a leading cause of death in persons with CF. Oral streptococcal colonization has been associated with stable CF lung function. However, no studies have demonstrated how Streptococcus salivarius, the most abundant streptococcal species found in individuals with stable CF lung disease, potentially improves lung function or becomes incorporated into the CF airway biofilm. By utilizing a two-species biofilm model to probe interactions between S. salivarius and P. aeruginosa, we discovered that the P. aeruginosa exopolysaccharide Psl promoted S. salivarius biofilm formation. Further, we identified a S. salivarius maltose-binding protein (MalE) that is required for promotion of biofilm formation both in vitro and in a Drosophila melanogaster co-infection model. Finally, we demonstrate that promotion of dual biofilm formation with S. salivarius is common among environmental and clinical P. aeruginosa isolates. Overall, our data supports a model in which S. salivarius uses a sugar-binding protein to interact with P. aeruginosa exopolysaccharide, which may be a strategy by which S. salivarius establishes itself within the CF airway microbial community.

Novel functional insights into a modified sugar-binding protein from Synechococcus MITS9220

Paradigms of metabolic strategies employed by photoautotrophic marine picocyanobacteria have been challenged in recent years. Based on genomic annotations, picocyanobacteria are predicted to assimilate organic nutrients via ATP-binding cassette importers, a process mediated by substrate-binding proteins. We report the functional characterisation of a modified sugar-binding protein, MsBP, from a marine Synechococcus strain, MITS9220. Ligand screening of MsBP shows a specific affinity for zinc (KD ~ 1.3 μM) and a preference for phosphate-modified sugars, such as fructose-1,6-biphosphate, in the presence of zinc (KD ~ 5.8 μM). Our crystal structures of apo MsBP (no zinc or substrate-bound) and Zn-MsBP (with zinc-bound) show that the presence of zinc induces structural differences, leading to a partially-closed substrate-binding cavity. The Zn-MsBP structure also sequesters several sulphate ions from the crystallisation condition, including two in the binding cleft, appropriately placed to mimic the orientation of adducts of a biphosphate hexose. Combined with a previously unseen positively charged binding cleft in our two structures and our binding affinity data, these observations highlight novel molecular variations on the sugar-binding SBP scaffold. Our findings lend further evidence to a proposed sugar acquisition mechanism in picocyanobacteria alluding to a mixotrophic strategy within these ubiquitous photosynthetic bacteria.

A DasA family sugar binding protein Ste2 links nutrient and oxidative stress to exopolysaccharides production in Streptomyces sp. 139

BackgroundEbosin is an exopolysaccharide produced by Streptomyces sp. 139, and its biosynthetic gene cluster (ste) has been previously described. Ste234 has high homology to the well-known ATP-binding cassette transport system DasABC, which has been linked to the regulation of morphological differentiation, antibiotics biosynthesis and aminosugars utilization in Streptomycetes. This study was conducted to evaluate the effect of the DasA family sugar binding protein Ste2 on Streptomyces sp. 139.ResultsThe disruption of ste2 results in the upregulation of transcription of genes within Ebosin biosynthetic gene cluster and a two-fold increase in Ebosin production. RNA sequencing data suggests that the disruption of ste2 results in the decreased utilization of carbon and nitrogen sources, increased sensitivity to oxidative stress, as well as differed strain morphology, all of which have been experimentally proven.ConclusionsTaken together, Ste2 controls Ebosin yields, aminosugars uptake, sensitivity to oxidative stress, and morphological differentiation of Streptomyces sp. 139.

Structure and Carbohydrate Recognition by the Nonmitogenic Lectin Horcolin.

Lectins are sugar-binding proteins that have shown considerable promise as antiviral agents because of their ability to interact with envelope glycoproteins present on the surface of viruses such as HIV-1. However, their therapeutic potential has been compromised by their mitogenicity that stimulates uncontrolled division of T-lymphocytes. Horcolin, a member of the jacalin family of lectins, tightly binds the HIV-1 envelope glycoprotein gp120 and neutralizes HIV-1 particles but is nonmitogenic. In this report, we combine X-ray crystallography and NMR spectroscopy to obtain atomic-resolution insights into the structure of horcolin and the molecular basis for its carbohydrate recognition. Each protomer of the horcolin dimer adopts a canonical β-prism I fold with three Greek key motifs and carries two carbohydrate-binding sites. The carbohydrate molecule binds in a negatively charged pocket and is stabilized by backbone and side chain hydrogen bonds to conserved residues in the ligand-binding loop. NMR titrations reveal a two-site binding mode and equilibrium dissociation constants for the two binding sites determined from two-dimensional (2D) lineshape modeling are 4-fold different. Single-binding-site variants of horcolin confirm the dichotomy in binding sites and suggest that there is allosteric communication between the two sites. An analysis of the horcolin structure shows a network of hydrogen bonds linking the two carbohydrate-binding sites directly and through a secondary binding site, and this coupling between the two sites is expected to assume importance in the interaction of horcolin with high-mannose glycans found on viral envelope glycoproteins.

Galectin-9 recognizes and exhibits antimicrobial activity toward microbes expressing blood group–like antigens

While adaptive immunity recognizes a nearly infinite range of antigenic determinants, immune tolerance renders adaptive immunity vulnerable to microbes decorated in self-like antigens. Recent studies suggest that sugar-binding proteins galectin-4 and galectin-8 bind microbes expressing blood group antigens. However, the binding profile and potential antimicrobial activity of other galectins, particularly galectin-9 (Gal-9), has remained incompletely defined. Here, we demonstrate that while Gal-9 possesses strong binding preference for ABO(H) blood group antigens, each domain exhibits distinct binding patterns, with the C-terminal domain (Gal-9C) exhibiting higher binding to blood group B than the N-terminal domain (Gal-9N). Despite this binding preference, Gal-9 readily killed blood group B–positive Escherichia coli, whereas Gal-9N displayed higher killing activity against this microbe than Gal-9C. Utilization of microarrays populated with blood group O antigens from a diverse array of microbes revealed that Gal-9 can bind various microbial glycans, whereas Gal-9N and Gal-9C displayed distinct and overlapping binding preferences. Flow cytometric examination of intact microbes corroborated the microbial glycan microarray findings, demonstrating that Gal-9, Gal-9N, and Gal-9C also possess the capacity to recognize distinct strains of Providencia alcalifaciens and Klebsiella pneumoniae that express mammalian blood group–like antigens while failing to bind related strains that do not express mammalian-like glycans. In each case of microbial binding, Gal-9, Gal-9N, and Gal-9C induced microbial death. In contrast, while Gal-9, Gal-9N, and Gal-9C engaged red blood cells, each failed to induce hemolysis. These data suggest that Gal-9 recognition of distinct microbial strains may provide antimicrobial activity against molecular mimicry.

Tobramycin-loaded complexes to prevent and disrupt Pseudomonas aeruginosa biofilms.

Carbohydrate-based materials are increasingly investigated for a range of applications spanning from healthcare to advanced functional materials. Synthetic glycopolymers are particularly attractive as they possess low toxicity and immunogenicity and can be used as multivalent ligands to target sugar-binding proteins (lectins). Here, we utilised RAFT polymerisation to synthesize two families of novel diblock copolymers consisting of a glycopolymers block containing either mannopyranose or galactopyranose pendant units, which was elongated with sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS) to generate a polyanionic block. The latter enabled complexation of cationic aminoglycoside antibiotic tobramycin through electrostatic interactions (loading efficiency in the 0.5-6.3 wt% range, depending on the copolymer). The resulting drug vectors were characterized by dynamic light scattering, zeta-potential, and transmission electron microscopy. Tobramycin-loaded complexes were tested for their ability to prevent clustering or disrupt biofilm of the Pseudomonas aeruginosa Gram-negative bacterium responsible for a large proportion of nosocomial infection, especially in immunocompromised patients. P. aeruginosa possesses two specific tetrameric carbohydrate-binding adhesins, LecA (PA-IL, galactose/N-acetyl-D-galactosamine-binding) and LecB (PA-IIL, fucose/mannose-binding), and the cell-associated and extracellular adhesin CdrA (Psl/mannose-binding) thus ideally suited for targeted drug delivery using sugar-decorated tobramycin-loaded complexes here developed. Both aliphatic and aromatic linkers were utilised to link the sugar pendant units to the polyacrylamide polymer backbone to assess the effect of the nature of such linkers on bactericidal/bacteriostatic properties of the complexes. Results showed that tobramycin-loaded complexes efficiently suppressed (40 to 60% of inhibition) in vitro biofilm formation in PAO1-L P. aeruginosa and that preferential targeting of PAO1-L biofilm can be achieved using mannosylated glycopolymer-b-AMPSm.

Oligosaccharide-lactoferrin shell-crosslinked particles for selective targeting of proteins to probiotic bacteria in the colon

Consumption of prebiotics seems to be a more effective approach for improving health compared to consumption of probiotic bacteria. However, these beneficial microorganisms require proteins to proliferate, while most consumed protein does not reach the gut. Still, no protein-containing prebiotics are commercially-available. Probiotic bacteria express sugar-binding-proteins (SBP) on their cell-membrane that mediate uptake of prebiotic oligosaccharides (OS). We have recently shown that Galactooligosaccharide-Lactoferrin hydrolysate (GOS-LFH) Maillard conjugates can serve as a vehicle for targeted delivery of protein to a model probiotic bacterium (Lactobacillus casei), boosting its growth rate. Herein, we aimed to advance this targeted protein delivery system by preparing three different compositions of prebiotic OS-LFH (2′-Fucosyllactose-LFH (2′-FL-LFH), Fructooligosaccharide-LFH (FOS-LFH), and Xylooligosaccharide-LFH (XOS-LFH)) self-assembled micellar particles, and characterizing their structure, physicochemical properties, and in-vitro digestibility. The OS shell of the particles is the molecular-recognition ligand for selective targeting to probiotic's SBP, and a shield against premature digestion of the delivered protein. We have demonstrated that these OS-LFH conjugates self-assembled into 10–25 nm particles, exhibiting good colloidal stability and lower susceptibility to proteolysis compared to the native lactoferrin (LF). Shell-crosslinking significantly reduced in-vitro gastrointestinal digestibility of the protein core. The proteolysis of the crosslinked 2′-FL-LFH, FOS-LFH, XOS-LFH progressed to only 55%, 57%, and 68% respectively, compared to native LF. Collectively, our findings suggest that these OS-LFH particles embody a promising strategy for high endurance and selective targeted delivery of protein to gut probiotics, which may enhance their competitive edge over non-beneficial/harmful colon bacteria, thereby promoting their potential to improve health.

Affinity Series of Genetically Encoded Förster Resonance Energy-Transfer Sensors for Sucrose.

Genetically encoded fluorescent sugar sensors are valuable tools for the discovery of transporters and for quantitative monitoring of sugar steady-state levels in intact tissues. Genetically encoded Förster resonance energy-transfer sensors for glucose have been designed and optimized extensively, and a full series of affinity mutants is available for in vivo studies. However, to date, only a single improved sucrose sensor FLIPsuc-90μΔ1 with Km for sucrose of ∼90 μM was available. This sucrose sensor was engineered on the basis of an Agrobacterium tumefaciens sugar-binding protein. Here, we took a two-step approach to first improve the dynamic range of the FLIPsuc sensor and then expand the detection range from micro- to millimolar sucrose concentrations by mutating a key residue in the binding site. The resulting series of sucrose sensors may enable investigation of sucrose transporter candidates and comprehensive in vivo analyses of sucrose concentration in plants. Since FLIPsuc-90μ also detects trehalose in animal cells, the new series of sensors will likely be suitable for investigating trehalose transport and monitor trehalose steady-state levels in vivo.

Glyco-Nanoadjuvants: Sugar Structures on Carriers of a Small Molecule TLR7 Ligand Affect Their Immunostimulatory Activities.

Toll-like receptors (TLRs) are pattern recognition receptors that activate innate immunity, and their ligands are promising adjuvants for vaccines and immunotherapies. Small molecule TLR7 ligands are ideal vaccine adjuvants as they induce not only proinflammatory cytokines but also type I interferons. However, their application has only been approved for local administration due to severe systemic immune-related adverse events. In a previous study, we prepared the gold nanoparticles coimmobilized with synthetic small molecule TLR7 ligand, 1V209, and α-mannose (1V209-αMan-GNPs). 1V209-αMan-GNPs were selectively delivered via a cell surface sugar-binding protein, mannose receptor, which enabled selective delivery of TLR7 ligands to immune cells. Besides the mannose receptor, immune cells express various sugar-binding proteins such as macrophage galactose binding lectins and sialic acid-binding immunoglobulin-type lectins and recognize distinct sugar structures. Hence, in the present study, we investigated whether sugar structures on GNPs affect the efficiency and selectivity of intracellular delivery and subsequent immunostimulatory potencies. Five neutral sugars and two sialosides were selected and each sugar was coimmobilized with 1V209 onto GNPs (1V209-SGNPs) and their innate immunostimulatory potencies were compared to that of 1V209-αMan-GNPs. The in vitro study using mouse bone marrow derived dendritic cells (BMDCs) demonstrated that α-glucose, α-N-acetylglucosamine, or α-fucose immobilized 1V209-SGNPs increased interleukin-6 and type I interferon release similar to that of 1V209-αMan-GNPs, whereas galacto-type sugar immobilized 1V209-SGNPs predominantly enhanced type I interferon release. In contrast, sialoside immobilized 1V209-SGNPs did not enhance the potency of 1V209. In the in vivo immunization study using ovalbumin as a model antigen, neutral sugar immobilized 1V209-SGNPs induced comparable T helper-1 immune response to that of 1V209-αMan-GNPs and by 10-fold higher than that of sialoside immobilized 1V209-SGNPs. These results indicate that the sugar structures on 1V209-SGNPs affect their immunostimulatory activities, and functionalization of the carrier particles is important to shape immune responses.

Glycolipid-dependent and lectin-driven transcytosis in mouse enterocytes

Glycoproteins and glycolipids at the plasma membrane contribute to a range of functions from growth factor signaling to cell adhesion and migration. Glycoconjugates undergo endocytic trafficking. According to the glycolipid-lectin (GL-Lect) hypothesis, the construction of tubular endocytic pits is driven in a glycosphingolipid-dependent manner by sugar-binding proteins of the galectin family. Here, we provide evidence for a function of the GL-Lect mechanism in transcytosis across enterocytes in the mouse intestine. We show that galectin-3 (Gal3) and its newly identified binding partner lactotransferrin are transported in a glycosphingolipid-dependent manner from the apical to the basolateral membrane. Transcytosis of lactotransferrin is perturbed in Gal3 knockout mice and can be rescued by exogenous Gal3. Inside enterocytes, Gal3 is localized to hallmark structures of the GL-Lect mechanism, termed clathrin-independent carriers. These data pioneer the existence of GL-Lect endocytosis in vivo and strongly suggest that polarized trafficking across the intestinal barrier relies on this mechanism.

Structural Studies on Different Ligand Binding Ability of Sialoadhesin Using Molecular Modeling Techniques

Siglecs are the major homologous subfamily of I-type lectins with an ability to recognize sialylated glycans. Siglecs are attractive therapeutic targets because of their endocytic properties, ability to modulate receptor signaling and cell-type specific expression pattern. Sialoadhesin (Sn/Siglec-1/CD169), a member of the Siglec family expressed on subsets of resident and inflammatory macrophages and involves in modulation of inflammation and immunity. In this work, 3-D structure of human Siglec-1 (hSiglec-1) was predicted based on X-ray crystallo-graphically determined structure of mouse Siglec-1[mSiglec-1(PDB ID: 1QFP)] using molecular modeling techniques. The structure of complexes in solution of hSiglec-1 with ligands, glycopeptide and 3′-sialyllactose were predicted using a novel docking technique comprising of repeated cycles of molecular dynamics and energy minimization. Calculation of the free energies of binding of complexes suggested that glycopeptide can form stable complex with dissociation constant value of 3.31 μM whereas complex formation of 3′-sialyllactose with the protein in aqueous medium is thermodynamically unfavorable. The structural analysis of theses complexes represent the functional recognition interactions of this protein with the bound sugar molecule and as such provide detailed information about functional roles of such sugar binding protein.

Regulation of mucosal lectins in the oyster Crassostrea virginica in response to food availability and environmental factors

ABSTRACT Lectins are a large and diverse group of sugar-binding proteins involved in nonself recognition and cell-to-cell interactions. Suspension-feeding bivalves, such as the oyster Crassostrea virginica, are capable of using these molecules to bind cell surface carbohydrates of food particles, allowing particle capture and selection. The aim of this project was to assess whether the expression of mucosal lectins in C. virginica is constant or changes with the season, and to determine whether lectin expression is linked to environmental parameters and/or internal biological factors (gametogenesis). A total of 130 oysters were placed in submerged cages at a tidal estuary and monitored for changes in lectin gene expression over a 1-year period. In parallel, environmental parameters prevailing at the field site, including seawater physicochemical characteristics (temperature, salinity and dissolved oxygen), particulate organic matter and chlorophyll contents, were also monitored. Throughout the study, oysters were dissected and the gills were collected and used for the assessment of the expression of three different lectin genes (CvML, CvML3914 and CvML3912). Remaining tissues were processed for histology and the classification of the gonad development stage. Results showed that when food is abundant, such as during the spring bloom, lectin gene expressions are low, and inversely lectin levels increase with lower food levels. These findings suggest that oysters increase lectin expression to enhance the capture and ingestion of scarce food, while during spring, enough food is already being ingested and lectins are not needed. Furthermore, results showed that as the energy demands of oysters increase (gonad maturation), lectin gene expressions also increase to enhance selective ingestion of nutritious food particles. This study, therefore, demonstrates the seasonality of lectin gene expression in C. virginica, and suggests that lectin regulation is related to the reproduction process and abundance of high-quality food.

Blood group systems

Blood group systems

LGALS3 Is a Poor Prognostic Factor in Diffusely Infiltrating Gliomas and Is Closely Correlated With CD163+ Tumor-Associated Macrophages.

Background: Glioma, the most common brain tumor, is a heterogeneous group of glia-derived tumors, the majority of which have characteristics of diffuse infiltration and immunosuppression. The LGALS protein family is a large class of sugar-binding proteins. Among them, LGALS3 has been reported to promote tumor development and progression in some cancers. However, the clinical significance and biological functions of LGALS3 in glioma remain virtually unknown. The purpose of our research is to detect LGALS3 expression and its prognostic value in glioma and reveal the relationship between its expression and the clinico/molecular-pathological features of patients and immune cell infiltration.Methods: LGALS3 protein expression was examined by immunohistochemistry. The mRNA expression data of LGALS3 was downloaded and analyzed from TCGA and Rembrandt datasets. The association between LGALS3 and glioma clinically relevant diagnostic/molecular markers (IDH, 1p19q, ATRX, MGMT, and TERT) was examined using the Chi-Squared (χ2) test. The correlation between LGALS3 expression and the infiltration of multiple intra-tumoral immune cell types, including B cells (CD20), T cells (CD4 and CD8), macrophages (CD68), and M2 tumor-associated macrophages (CD163), was evaluated by Spearman correlation analysis. Kaplan-Meier analysis and the Cox regression analysis were applied to evaluate the prognostic value of LGALS3 in glioma. The log-rank test was used to evaluate Kaplan-Meier results for significance.Results: Out of all 304 glioma cases, LGALS3 protein was expressed in 125 glioma cases (41.1%, 125/304), with 69.2% (9/13) in WHO I, 9.8% (8/82) in WHO II, 34.2% (26/76) in WHO III, and 61.7% (82/133) in WHO IV. The expression of LGALS3 was correlated with patient age, WHO grade, PHH3 (mitosis), Ki67 index, IDH, 1p/19q codeletion, and TERT promoter status. LGALS3 was an independent poor prognostic marker in diffusely infiltrating gliomas and was positively correlated with immune cell infiltration, particularly CD163+ tumor-associated macrophages in the TCGA dataset, Rembrandt dataset, and our SYSUCC cohort (R = 0.419, 0.627, and 0.724).Conclusion: LGALS3 was highly expressed in pilocytic astrocytoma, GBM, and IDH wild-type LGG. It served as a poor prognostic marker in diffusely infiltrating gliomas. Based on its prognostic significance and strong correlation with CD163+ TAMs, it may act as an important therapeutic target for human glioma.

Caveolin-1 Modulation Increases Efficacy of a Galacto-Conjugated Phthalocyanine in Bladder Cancer Cells Resistant to Photodynamic Therapy.

Photodynamic therapy (PDT) has demonstrated encouraging anticancer therapeutic results, but the current clinically approved photosensitizers (PSs) are not ideal in the treatment of bladder cancer. Conventional PSs have low selectivity to the bladder tumor tissue and induce toxicity or bystander effects on nontumor urothelium. Previous studies demonstrated that the use of galactose-photosensitizer (PS) conjugates is a more selective method of delivering PDT-mediated toxicity due to their ability to recognize carbohydrate-binding domains overexpressed in bladder tumors. Using patient-derived bladder tumor specimens cultured ex vivo and bladder cancer cell lines with different PDT sensitivity, we find that a galactose-phthalocyanine (PcGal16) accumulates in bladder tumors expressing galactose-binding proteins and internalizes through an endocytic process. The endocytosis mechanism is cell line-dependent. In HT-1376 bladder cancer lines resistant to PDT, depletion of caveolin-1-the main structural protein of caveolae structures-increased the amount of sugar-binding proteins, i.e. GLUT1, at the cell membrane resulting in an improved PcGal16 uptake and PDT efficacy. These data show the potential of ex vivo cultures of bladder cancer, that ideally could mimic the original microenvironment, in screening galacto-PDT agents. Additionally, our studies demonstrate that PDT efficacy in bladder cancer depends on the endocytic mechanisms that regulate PS accumulation and internalization in cancer cells.

Bacterial sugar-binding protein as a one-step affinity purification tag on dextran-containing resins

Marinobacter hydrocarbonoclasticus is an oil-eating bacterium that possesses a large adhesion protein (MhLap) with the potential to bind extracellular ligands. One of these ligand-binding modules is the ~20-kDa PA14 domain (MhPA14) that has affinity for glucose-based carbohydrates. Previous studies showed this sugar-binding domain is retained on dextran-based size-exclusion resins during chromatography, requiring the introduction of glucose or EDTA to remove the protein from the column. Given the ready availability of such size-exclusion resins in biochemistry laboratories, this study explores the use of MhPA14 as an affinity tag for recombinant protein purification. Two different fusion proteins were tested: 1) Green fluorescent protein (GFP) linked to the N-terminus of the MhPA14 tag; and 2) the ice-binding domain from the Marinomonas primoryensis ice-binding protein (MpIBD) linked to the MhPA14 C-terminus by a TEV cut site. The GFP_MhPA14 fusion visibly bound to Superdex, Sephadex, and Sephacryl resins, but did not bind to Sepharose. Using Superdex resin, dextran-affinity purification proved to be an effective one-step purification strategy for both proteins, superior to even nickel-affinity chromatography. Dextran-affinity chromatography was also the most effective method of separating the MhPA14 tag from MpIBD following TEV proteolysis, as compared to both nickel-affinity and ice-affinity methods. These results indicate that MhPA14 has potential for widespread use in recombinant protein purification.

Diversiform and Transformable Glyco-Nanostructures Constructed from Amphiphilic Supramolecular Metallocarbohydrates through Hierarchical Self-Assembly: The Balance between Metallacycles and Saccharides.

During the past decade, self-assembly of saccharide-containing amphiphilic molecules toward bioinspired functional glycomaterials has attracted continuous attention due to their various applications in fundamental and practical areas. However, it still remains a great challenge to prepare hierarchical glycoassemblies with controllable and diversiform structures because of the complexity of saccharide structures and carbohydrate-carbohydrate interactions. Herein, through hierarchical self-assembly of modulated amphiphilic supramolecular metallocarbohydrates, we successfully prepared various well-defined glyco-nanostructures in aqueous solution, including vesicles, solid spheres, and opened vesicles depending on the molecular structures of metallocarbohydrates. More attractively, these glyco-nanostructures can further transform into other morphological structures in aqueous solutions such as worm-like micelles, tubules, and even tupanvirus-like vesicles (TVVs). It is worth mentioning that distinctive anisotropic structures including the opened vesicles (OVs) and TVVs were rarely reported in glycobased nano-objects. This intriguing diversity was mainly controlled by the subtle structural trade-off of the two major components of the amphiphiles, i.e., the saccharides and metallacycles. To further understand this precise structural control, molecular simulations provided deep physical insights on the morphology evolution and balancing of the contributions from saccharides and metallacycles. Moreover, the multivalency of glyco-nanostructures with different shapes and sizes was demonstrated by agglutination with a diversity of sugar-binding protein receptors such as the plant lectins Concanavalin A (ConA). This modular synthesis strategy provides access to systematic tuning of molecular structure and self-assembled architecture, which undoubtedly will broaden our horizons on the controllable fabrication of biomimetic glycomaterials such as biological membranes and supramolecular lectin inhibitors.

Preliminary Characterization of Crude Lectins Fractions of Red Macroalgae Species Collected from the Southern Coast of Gunungkidul Indonesia

Lectins or hemagglutininsare specific sugar-binding proteins (glycoproteins) of non-immune origins that typically agglutinate certain cells and/or precipitate glycoconjugates. This study aimed to evaluate the activity of hemagglutination, protein comtent, and initial characterization (the stability towards pH, temperature, divalent cation and inhibition of hemagglutination activity by sugars and/or glycoproteins) crude lectins fractions of red macroalgae from the coast of Gunungkidul Beach, Yogyakarta. The findings showed that hemagglutination activity using trypsin treated rabbit erythrocytes of crude fractions of red algae lectins Nitophylium punctatum species, Helminthora divaricata, and Acanthophora spicifera were 26, 26, and 213, respectively. The protein contents were 8,123.47 μg / ml; 9,545.65 μg / ml; and 7,368.45 μg / ml. Although the three red macroalgae species tend to maintain a relatively stable pH, their temperature tolerance was unstable, and were unaffected by divalent cations. The carbohydrate-binding specificities assay of the red macroalgae species showed the occcurence of inhibition in certain glycoproteins and not simple sugars.

Encoding biological recognition in a bicomponent cell-membrane mimic

Self-assembling dendrimers have facilitated the discovery of periodic and quasiperiodic arrays of supramolecular architectures and the diverse functions derived from them. Examples are liquid quasicrystals and their approximants plus helical columns and spheres, including some that disregard chirality. The same periodic and quasiperiodic arrays were subsequently found in block copolymers, surfactants, lipids, glycolipids, and other complex molecules. Here we report the discovery of lamellar and hexagonal periodic arrays on the surface of vesicles generated from sequence-defined bicomponent monodisperse oligomers containing lipid and glycolipid mimics. These vesicles, known as glycodendrimersomes, act as cell-membrane mimics with hierarchical morphologies resembling bicomponent rafts. These nanosegregated morphologies diminish sugar-sugar interactions enabling stronger binding to sugar-binding proteins than densely packed arrangements of sugars. Importantly, this provides a mechanism to encode the reactivity of sugars via their interaction with sugar-binding proteins. The observed sugar phase-separated hierarchical arrays with lamellar and hexagonal morphologies that encode biological recognition are among the most complex architectures yet discovered in soft matter. The enhanced reactivity of the sugar displays likely has applications in material science and nanomedicine, with potential to evolve into related technologies.

Lectin engineering: the possible and the actual.

Lectins are a widespread group of sugar-binding proteins occurring in all types of organisms including animals, plants, bacteria, fungi and even viruses. According to a recent report, there are more than 50 lectin scaffolds (∼Pfam), for which three-dimensional structures are known and sugar-binding functions have been confirmed in the literature, which far exceeds our view in the twentieth century (Fujimoto et al. 2014 Methods Mol. Biol. 1200, 579-606 (doi:10.1007/978-1-4939-1292-6_46)). This fact suggests that new lectins will be discovered either by a conventional screening approach or just by chance. It is also expected that new lectin domains including those found in enzymes as carbohydrate-binding modules will be generated in the future through evolution, although this has never been attempted on an experimental level. Based on the current state of the art, various methods of lectin engineering are available, by which lectin specificity and/or stability of a known lectin scaffold can be improved. However, the above observation implies that any protein scaffold, including those that have never been described as lectins, may be modified to acquire a sugar-binding function. In this review, possible approaches to confer sugar-binding properties on synthetic proteins and peptides are described.