Isolation and characterization of glycoprotein lectins from the bark of three species of elder, Sambucus ebulus, S. nigra and S. racemosa

VOLKSMED Database: A Source for Forgotten Wound Healing Plants in Austrian Folk Medicine

The global increase in the incidence of wounds is concerning and fuels the search for new treatment options. The use of traditional medicinal plants in wound healing represents an appreciated available therapeutic possibility. This work introduces the VOLKSMED database, which contains plants and other materials used in Austrian folk medicine, either as monographs or mixtures. This work focuses on the monographs of the database. Concerning wound healing, Hypericum sp., Arnica montana, Calendula officinalis, Plantago sp., and Malva sp. are the most commonly used plants. The focus of this paper is set on selected lesser-known plants (Abies alba, Anthyllis vulneraria, Brassica sp., Gentiana sp., Larix decidua, Picea abies, Sambucus sp., Sanicula europaea) and their status quo in literature concerning wound healing. A systematic search using the databases SciFinder, SCOPUS, and PubMed yielded substantial evidence for the wound healing potential of Brassica sp., Gentiana sp., the Pinaceae A. abies, L. decidua, and P. abies, as well as Sambucus nigra. In vivo and clinical studies substantiate their use in Austrian folk medicine. According to the literature, especially A. vulneraria, Sambucus racemosa, and S. europaea would be worth investigating in-depth since data concerning their wound healing effects - even though scarce - are convincing. In conclusion, the VOLKSMED database contains promising opportunities for further treatment options in the field of wound healing. Future research should consider the listed plants to support their traditional use in Austrian folk medicine and possibly promote the implementation of old knowledge in modern medicine.

Combined Bacteria Microarray and Quartz Crystal Microbalance Approach for Exploring Glycosignatures of Nontypeable Haemophilus influenzae and Recognition by Host Lectins

Recognition of bacterial surface epitopes by host receptors plays an important role in the infectious process and is intimately associated with bacterial virulence. Delineation of bacteria-host interactions commonly relies on the detection of binding events between purified bacteria- and host-target molecules. In this work, we describe a combined microarray and quartz crystal microbalance (QCM) approach for the analysis of carbohydrate-mediated interactions directly on the bacterial surface, thus preserving the native environment of the bacterial targets. Nontypeable Haemophilus influenzae (NTHi) was selected as a model pathogenic species not displaying a polysaccharide capsule or O-antigen-containing lipopolysaccharide, a trait commonly found in several important respiratory pathogens. Here, we demonstrate the usefulness of NTHi microarrays for exploring the presence of carbohydrate structures on the bacterial surface. Furthermore, the microarray approach is shown to be efficient for detecting strain-selective binding of three innate immune lectins, namely, surfactant protein D, human galectin-8, and Siglec-14, to different NTHi clinical isolates. In parallel, QCM bacteria-chips were developed for the analysis of lectin-binding kinetics and affinity. This novel QCM approach involves capture of NTHi on lectin-derivatized chips followed by formaldehyde fixation, rendering the bacteria an integrated part of the sensor chip, and subsequent binding assays with label-free lectins. The binding parameters obtained for selected NTHi-lectin pairs provide further insights into the interactions occurring at the bacterial surface.

Ribosome-inactivating and related proteins

Ribosome-inactivating proteins (RIPs) are toxins that act as N-glycosidases (EC 3.2.2.22). They are mainly produced by plants and classified as type 1 RIPs and type 2 RIPs. There are also RIPs and RIP related proteins that cannot be grouped into the classical type 1 and type 2 RIPs because of their different sizes, structures or functions. In addition, there is still not a uniform nomenclature or classification existing for RIPs. In this review, we give the current status of all known plant RIPs and we make a suggestion about how to unify those RIPs and RIP related proteins that cannot be classified as type 1 or type 2 RIPs.

Ebulin from dwarf elder (Sambucus ebulus L.): a mini-review

Sambucus ebulus L. (dwarf elder) is a medicinal plant, the usefulness of which also as food is restricted due to its toxicity. In the last few years, both the chemistry and pharmacology of Sambucus ebulus L. have been investigated. Among the structural and functional proteins present in the plant, sugar-binding proteins (lectins) with or without anti-ribosomal activity and single chain ribosome-inactivating proteins (RIPs) have been isolated. RIPs are enzymes (E.C. 3.2.2.22) that display N-glycosidase activity on the 28S rRNA subunit, leading to the inhibition of protein synthesis by arresting the step of polypeptide chain elongation. The biological role of all these proteins is as yet unknown. The evidence suggests that they could be involved in the defense of the plant against predators and viruses or/and a nitrogen store, with an impact on the nutritional characteristics and food safety. In this mini-review we describe all the isoforms of ebulin that have to date been isolated from dwarf elder, as well as their functional characteristics and potential uses, whilst highlighting concern regarding ebulin toxicity.

Elderberries: a source of ribosome-inactivating proteins with lectin activity

Sambucus (Adoxaceae) species have been used for both food and medicine purposes. Among these, Sambucus nigra L. (black elder), Sambucus ebulus L. (dwarf elder), and Sambucus sieboldiana L. are the most relevant species studied. Their use has been somewhat restricted due to the presence of bioactive proteins or/and low molecular weight compounds whose ingestion could trigger deleterious effects. Over the last few years, the chemical and pharmacological characteristics of Sambucus species have been investigated. Among the proteins present in Sambucus species both type 1, and type 2 ribosome-inactivating proteins (RIPs), and hololectins have been reported. The biological role played by these proteins remains unknown, although they are conjectured to be involved in defending plants against insect predators and viruses. These proteins might have an important impact on the nutritional characteristics and food safety of elderberries. Type 2 RIPs are able to interact with gut cells of insects and mammals triggering a number of specific and mostly unknown cell signals in the gut mucosa that could significantly affect animal physiology. In this paper, we describe all known RIPs that have been isolated to date from Sambucus species, and comment on their antiviral and entomotoxic effects, as well as their potential uses.

Two distinct jacalin-related lectins with a different specificity and subcellular location are major vegetative storage proteins in the bark of the black mulberry tree

Using a combination of protein isolation/characterization and molecular cloning, we have demonstrated that the bark of the black mulberry tree (Morus nigra) accumulates large quantities of a galactose-specific (MornigaG) and a mannose (Man)-specific (MornigaM) jacalin-related lectin. MornigaG resembles jacalin with respect to its molecular structure, specificity, and co- and posttranslational processing indicating that it follows the secretory pathway and eventually accumulates in the vacuolar compartment. In contrast, MornigaM represents a novel type of highly active Man-specific jacalin-related lectin that is synthesized without signal peptide or other vacuolar targeting sequences, and accordingly, accumulates in the cytoplasm. The isolation and cloning, and immunocytochemical localization of MornigaG and MornigaM not only demonstrates that jacalin-related lectins act as vegetative storage proteins in bark, but also allows a detailed comparison of a vacuolar galactose-specific and a cytoplasmic Man-specific jacalin-related lectin from a single species. Moreover, the identification of MornigaM provides the first evidence, to our knowledge, that bark cells accumulate large quantities of a cytoplasmic storage protein. In addition, due to its high activity, abundance, and ease of preparation, MornigaM is of great potential value for practical applications as a tool and bioactive protein in biological and biomedical research.

A lectin from the bark of the rubber tree (Hevea brasiliensis)

A protein isolated and purified from extracts of bark strips from mature rubber (Hevea brasilinsis) agglutinated erythrocytes from rabbits and all human blood types except AB. No agglutination was detected with erythrocytes from sheep, rates or mice. Proteolytic treatment of Hevea bark lectin (HBL) abolished haemagglutinin activity. The M(r) determined by SDS-PAGE was 40 k and that estimated from gel filtration was 140 k. Fetuin, asialofetuin, bovine submaxillary mucin and asialosubmaxillary mucin inhibited HBL-induced agglutination of rabbit erythrocytes. The HBL showed maximum haemagglutination activity over the pH range 4.5-9.5 and heat stability up to 60 degrees.

The role of lectins in plant defence

Recent progress in the search for the physiological role of plant lectins supports the idea that some of these proteins are involved in the defence mechanisms of the plant. To place the evidence in favour of such a defensive role in a broad perspective, a short overview is given of the most important plant pathogens and predators. In addition, the solutions that plants have developed to resist the continuous threat of a hostile environment are briefly discussed in relation to the protective role of proteins in general. The presumed involvement of plant lectins in defence mechanisms is first inferred from an analysis of the biochemical, physiological, cellular biological and molecular biological properties of plant lectins. Subsequently, the available experimental evidence for the involvement of lectins in the plant's defence against viruses, bacteria, fungi and herbivorous invertebrates and vertebrates is discussed in some detail. Since the defensive role of plant lectins is determined largely by their ability to recognize and bind foreign glycans, a brief discussion is given of how the basically protective properties of these proteins can be exploited for histochemical applications in biological and biomedical research.

Cloning of a lectin cDNA and seasonal changes in levels of the lectin and its mRNA in the inner bark of Robinia pseudoacacia

A cDNA clone encoding a lectin was isolated by immunological screening of an expression library prepared from poly(A)+ RNA from the inner bark of Robinia pseudoacacia. The cDNA clone (RBL104) had an open reading frame of 858 bp that encoded a polypeptide with a predicted molecular weight of 31210. This molecular weight corresponded closely to that of a polypeptide immunoprecipitated from products of translation in vitro of the poly(A)+ RNA. Thus, RBL104 appeared to be a full-length cDNA. The N-terminal amino acid sequence of the purified lectin protein matched a portion of the predicted amino acid sequence. It appeared that the lectin was synthesized as a precursor that consisted of a putative signal peptide of 31 amino acids and a mature polypeptide of 255 amino acids. Southern blot analysis of the genomic DNA revealed that the lectin was encoded by a small multigene family. The lectin was mostly localized in the axial and ray parenchymal cells of the inner bark. A small amount of lectin was also found in the axial and ray parenchymal cells of the xylem. The lectin accumulated in the inner bark in September, remained at high levels during the winter and disappeared in May. The mRNA for the lectin was detected from August to the following March. The appearance and disappearance of the mRNA were observed prior to those of the lectin protein.

A comparison of the lectin-binding properties of glycoconjugates from a range of Leishmania species

Constituent glycoconjugates of promastigotes of 14 different Leishmania strains from 6 different species were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and subsequently stained with 14 125I-labelled lectins of different specificities. Autoradiography of the gels revealed lectin-specific glycoproteins and other glycoconjugates of known molecular weight. Similarities and differences in antigens and glycoproteins present in the strains are described. The possibility of identification or characterisation of Leishmania species from their electrophoretic behaviour and lectin-binding patterns is unlikely, but these results should be an aid to purification of glycoconjugates from particular strains by lectin-affinity chromatography.

Trypanosoma cruzi: studies on the interactions of lectins with glycoconjugates of different zymodemes

Detergent extracts were made of eight strains of Trypanosoma cruzi which were representative of the principal zymodemes. The extracts were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the glycoproteins were reacted with 21 different 125I-labeled lectins and autoradiographed. The staining patterns with particular lectins varied considerably between strains. Concanavalin A stained up to 17 distinct bands in some strains. Other lectins such as peanut lectin only stained two bands in zymodeme 1 strains and none in the other zymodemes. The reaction of N-acetylgalactosamine-specific lectins with some bands indicated the presence of this sugar and this was confirmed by analysis of the extracts. The lectin staining patterns provided an insight into the glycoprotein composition of the bands and should indicate whether combinations of lectins can be used in affinity chromatography systems to purify the glycoproteins.