Proteins with an Euonymus lectin-like domain are ubiquitous in Embryophyta

<p>Abstract</p> <p>Background</p> <p>Cloning of the <it>Euonymus </it>lectin led to the discovery of a novel domain that also occurs in some stress-induced plant proteins. The distribution and the diversity of proteins with an <it>Euonymus </it>lectin (EUL) domain were investigated using detailed analysis of sequences in publicly accessible genome and transcriptome databases.</p> <p>Results</p> <p>Comprehensive in silico analyses indicate that the recently identified <it>Euonymus europaeus </it>lectin domain represents a conserved structural unit of a novel family of putative carbohydrate-binding proteins, which will further be referred to as the <it>Euonymus </it>lectin (EUL) family. The EUL domain is widespread among plants. Analysis of retrieved sequences revealed that some sequences consist of a single EUL domain linked to an unrelated N-terminal domain whereas others comprise two in tandem arrayed EUL domains. A new classification system for these lectins is proposed based on the overall domain architecture. Evolutionary relationships among the sequences with EUL domains are discussed.</p> <p>Conclusion</p> <p>The identification of the EUL family provides the first evidence for the occurrence in terrestrial plants of a highly conserved plant specific domain. The widespread distribution of the EUL domain strikingly contrasts the more limited or even narrow distribution of most other lectin domains found in plants. The apparent omnipresence of the EUL domain is indicative for a universal role of this lectin domain in plants. Although there is unambiguous evidence that several EUL domains possess carbohydrate-binding activity further research is required to corroborate the carbohydrate-binding properties of different members of the EUL family.</p

Differences in the mannose oligomer specificities of the closely related lectins from Galanthus nivalis and Zea mays strongly determine their eventual anti-HIV activity

<p>Abstract</p> <p>Background</p> <p>In a recent report, the carbohydrate-binding specificities of the plant lectins <it>Galanthus nivalis </it>(GNA) and the closely related lectin from <it>Zea mays </it>(GNA_maize) were determined by glycan array analysis and indicated that GNA_maizerecognizes complex-type N-glycans whereas GNA has specificity towards high-mannose-type glycans. Both lectins are tetrameric proteins sharing 64% sequence similarity.</p> <p>Results</p> <p>GNA_maizeappeared to be ~20- to 100-fold less inhibitory than GNA against HIV infection, syncytia formation between persistently HIV-1-infected HuT-78 cells and uninfected CD4⁺T-lymphocyte SupT1 cells, HIV-1 capture by DC-SIGN and subsequent transmission of DC-SIGN-captured virions to uninfected CD4⁺T-lymphocyte cells. In contrast to GNA, which preferentially selects for virus strains with deleted high-mannose-type glycans on gp120, prolonged exposure of HIV-1 to dose-escalating concentrations of GNA_maizeselected for mutant virus strains in which one complex-type glycan of gp120 was deleted. Surface Plasmon Resonance (SPR) analysis revealed that GNA and GNA_maizeinteract with HIV III_Bgp120 with affinity constants (K_D) of 0.33 nM and 34 nM, respectively. Whereas immobilized GNA specifically binds mannose oligomers, GNA_maizeselectively binds complex-type GlcNAcβ1,2Man oligomers. Also, epitope mapping experiments revealed that GNA and the mannose-specific mAb 2G12 can independently bind from GNA_maizeto gp120, whereas GNA_maizecannot efficiently bind to gp120 that contained prebound PHA-E (GlcNAcβ1,2man specific) or SNA (NeuAcα2,6X specific).</p> <p>Conclusion</p> <p>The markedly reduced anti-HIV activity of GNA_maizecompared to GNA can be explained by the profound shift in glycan recognition and the disappearance of carbohydrate-binding sites in GNA_maizethat have high affinity for mannose oligomers. These findings underscore the need for mannose oligomer recognition of therapeutics to be endowed with anti-HIV activity and that mannose, but not complex-type glycan binding of chemotherapeutics to gp120, may result in a pronounced neutralizing activity against the virus.</p

Lectin domains at the frontiers of plant defense

Plants are under constant attack from pathogens and herbivorous insects. To protect and defend themselves, plants evolved a multi-layered surveillance system, known as the innate immune system. Plants sense their encounters upon perception of conserved microbial structures and damage-associated patterns using cell-surface and intracellular immune receptors. Plant lectins and proteins with one or more lectin domains represent a major part of these receptors. The whole group of plant lectins comprises an elaborate collection of proteins capable of recognizing and interacting with specific carbohydrate structures, either originating from the invading organisms or from damaged plant cell wall structures. Due to the vast diversity in protein structures, carbohydrate recognition domains and glycan binding specificities, plant lectins constitute a very diverse protein superfamily. In the last decade, new types of nucleocytoplasmic plant lectins have been identified and characterized, in particular lectins expressed inside the nucleus and the cytoplasm of plant cells often as part of a specific plant response upon exposure to different stress factors or changing environmental conditions. In this review, we provide an overview on plant lectin motifs used in the constant battle against pathogens and predators during plant defenses

Uncovering the genetic basis for early isogamete differentiation: a case study of Ectocarpus siliculosus

Background: The phenomenon of sexual reproduction characterizes nearly all eukaryotes, with anisogamy being the most prevalent form of gamete discrimination. Since dimorphic gametes most likely descend from equal-sized specialized germ cells, identifying the genetic bases of the early functional diversification in isogametes can provide better understanding of the evolution of sexual dimorphism. However, despite the potential importance to the evolutionary biology field, no comprehensive survey of the transcriptome profiling in isomorphic gametes has been reported hitherto. Results: Gamete differentiation on the genomic level was investigated using Ectocarpus siliculosus, a model organism for brown algal lineage which displays an isogamous sexual reproduction cycle. Transcriptome libraries of male and female gametes were generated using Next Generation Sequencing technology (SOLiD) and analyzed to identify differentially regulated genes and pathways with potential roles in fertilization and gamete specialization. Gamete transcriptomes showed a high level of complexity with a large portion of gender specific gene expression. Our results indicate that over 4,000 of expressed genes are differentially regulated between male and female, including sequences related to cell movement, carbohydrate and lipid metabolism, signaling, transport and RNA processing. Conclusions: This first comprehensive transcriptomic study of protist isogametes describes considerable adaptation to distinct sexual roles, suggesting that functional anisogamy precedes morphological differentiation. Several sex-biased genes and pathways with a putative role in reproduction were identified, providing the basis for more detailed investigations of the mechanisms underlying evolution of mating types and sexual dimorphism

Expression analysis of a type S2 EUL-related lectin from rice in Pichia pastoris

Rice (Oryza sativa) expresses different putative carbohydrate-binding proteins belonging to the class of lectins containing an Euonymus lectin (EUL)-related domain, one of them being OrysaEULS2. The OrysaEULS2 sequence consists of a 56 amino acid N-terminal domain followed by the EUL sequence. In this paper the original sequence of the EUL domain of OrysaEULS2 and some mutant forms have been expressed in Pichia pastoris. Subsequently, the recombinant proteins were purified and their carbohydrate binding properties determined. Analysis of the original protein on the glycan array revealed interaction with mannose containing structures and to a lesser extent with glycans containing lactosamine related structures. It was shown that mutation of tryptophan residue 134 into leucine resulted in an almost complete loss of carbohydrate binding activity of OrysaEULS2. Our results show that the EUL domain in OrysaEULS2 interacts with glycan structures, and hence can be considered as a lectin. However, the binding of the protein with the array is much weaker than that of other EUL-related lectins. Furthermore, our results indicate that gene divergence within the family of EUL-related lectins lead to changes in carbohydrate binding specificity.status: publishe

NICTABA and UDA, two GlcNAc-binding lectins with unique antiviral activity profiles

This study aimed to assess the antiviral properties of a unique lectin (NICTABA) produced by the tobacco plant, Nicotiana tabacum.status: publishe

HIV-1 envelope trimer has similar binding characteristics for carbohydrate-binding agents as monomeric gp120

The native HIV-1 Env complex consists of a gp120/gp41 trimer, but surface plasmon resonance (SPR)-directed binding studies for gp120-binding agents were almost exclusively performed on monomeric gp120. SPR-directed binding kinetics of monomeric gp120 and trimeric gp140 were investigated for a broad variety of envelope (Env)-binding agents. Similar kinetics for carbohydrate-binding agents (CBAs), the antibody 2G12 and sCD4 were observed, irrespective of the oligomeric state of gp120 that either contain the native mixture of complex and high-mannose N-glycans or that contain exclusively oligomannose N-glycans. The generally comparable kinetic properties of CBA, 2G12 and sCD4 binding to monomeric gp120 and trimeric gp140 indicate that monomeric gp120 is a good surrogate molecule for native HIV-1 Env trimer to investigate the binding affinities of Env-binding compounds. STRUCTURED SUMMARY OF PROTEIN INTERACTIONS: gp120binds to GRFT by surface plasmon resonance (View Interaction: 1, 2) gp120binds to UDA by surface plasmon resonance (View Interaction: 1, 2) gp120binds to AH by surface plasmon resonance (View Interaction: 1, 2).status: publishe

Inhibition of infection and transmission of HIV-1 and lack of significant impact on the vaginal commensal lactobacilli by carbohydrate-binding agents

Carbohydrate-binding agents (CBAs) have been shown to have an anti-HIV-1 activity by interacting with the glycans on the HIV-1 envelope glycoprotein gp120. We validated the antiviral activity of several CBAs, with various carbohydrate-recognition characteristics. It could be concluded that the CBAs inhibited at least 4 viral processes: cell-free virus infection of human CD4+ T-lymphocyte C8166 cells, giant-cell formation between persistently infected Hut-78/HIV-1 and CD4+ T-lymphocyte SupT1 cells, the capture of virus by DC-SIGN-expressing cells and the transmission of DC-SIGN-captured virus to C8166 cells. Therefore, these CBAs are attractive candidate compounds for the development of novel types of microbicides, meant to be administered topically to prevent HIV-1 transmission during sexual intercourse. It is important to ensure that these CBAs have no detrimental effects on the local vaginal microflora which consists mainly of a variety of Lactobacilli. We could demonstrate that none of the examined CBAs had a meaningful effect on the growth, adhesion and viability of several vaginal and non-vaginal Lactobacillus strains. In conclusion, our data emphasize and support the possibility of using CBAs for the development of novel microbicides, which could contribute to the prevention of HIV-1 infection.status: publishe