Biomedical subjects

A Barre

Publications and source records attributed to A Barre.

At least 37 records · Page 2Linked to original sources

PubMed1999

Isolation, characterization, molecular cloning and molecular modelling of two lectins of different specificities from bluebell (Scilla campanulata) bulbs.

Two lectins have been isolated from bluebell (Scilla campanulata) bulbs. From their isolation by affinity chromatography, they are characterized as a mannose-binding lectin (SCAman) and a fetuin-binding lectin (SCAfet). SCAman preferentially binds oligosaccharides with alpha(1,3)- and alpha(1,6)-linked mannopyranosides. It is a tetramer of four identical protomers of approx. 13 kDa containing 119 amino acid residues; it is not glycosylated. The fetuin-binding lectin (SCAfet), which is not inhibited by any simple sugars, is also unglycosylated. It is a tetramer of four identical subunits of approx. 28 kDa containing 244 residues. Each 28 kDa subunit is composed of two 14 kDa domains. Both lectins have been cloned from a cDNA library and sequenced. X-ray crystallographic analysis and molecular modelling studies have demonstrated close relationships in sequence and structure between these lectins and other monocot mannose-binding lectins. A refined model of the molecular evolution of the monocot mannose-binding lectins is proposed.

Amino Acid Sequence↗

PubMed1999

Homology modelling of the core domain of the endogenous lectin comitin: structural basis for its mannose-binding specificity.

The N-terminal core domain of comitin from the slime mold Dictyostelium discoideum has been modelled from the X-ray coordinates of the monocot mannose-binding lectin from snowdrop (Galanthus nivalis). Docking experiments performed on the three-dimensional model showed that two of the three mannose-binding sites of the comitin monomer are functional. They are located at both ends of the comitin dimer whereas the actin-interacting region occurs in the central hinge region where both monomers are non covalently associated. This distribution is fully consistent with the bifunctional character of comitin which is believed to link the Golgi vesicles exhibiting mannosylated membrane glycans to the actin cytoskeleton in the cell.

Amino Acid Sequence↗

PubMed1999

Characterization of the Arabidopsis lecRK-a genes: members of a superfamily encoding putative receptors with an extracellular domain homologous to legume lectins.

An Arabidopsis cDNA clone that defines a new class of plant serine/threonine receptor kinases was found to be a member of a family of four clustered genes (lecRK-a1-a4) which have been cloned, sequenced and mapped on chromosome 3. This family belongs to a large superfamily encoding putative receptors with an extracellular domain homologous to legume lectins and appears to be conserved at least among dicots. In the Columbia ecotype only the lecRK-a1 and perhaps the lecRK-a3 gene is functional, since lecRK-a2 is disrupted by a Ty-copia retroelement and lecRK-a4 contains a frameshift mutation. Structural analysis of the lecRK-al and lecRK-a3 deduced amino-acid sequences suggests that the lectin domain is unlikely to be involved in binding monosaccharides but could interact with complex glycans and/or with hydrophobic ligands. Immunodetection of lecRK gene products in plasma membranes purified by free-flow electrophoresis showed that the lecRK-a proteins are probably highly glycosylated integral plasma membrane components.

Amino Acid Sequence↗

PubMed1999

Characterization and molecular cloning of the lectin from Helianthus tuberosus.

A lectin called Helianthus tuberosus agglutinin or Heltuba has been isolated from tubers of the Jerusalem artichoke, a typical representative of the Asteraceae family. Heltuba is a tetrameric protein composed of four identical subunits of 15.5 kDa and exhibits a preferential specificity towards oligomannosides. Cloning of the corresponding cDNAs revealed that the mature lectin polypeptide comprises the entire open reading frame of the cDNA suggesting that the primary translation product is not processed and that the lectin is a cytosolic protein. Searches in the databases revealed sequence similarity with lectins from the taxonomically unrelated Convolvulaceae and Moraceae species. Therefore, the discovery of Heltuba is of great importance in view of the occurrence and molecular evolution of the jacalin-related lectins.

Agglutinins↗

PubMed1999

A gene encoding a hevein-like protein from elderberry fruits is homologous to PR-4 and class V chitinase genes.

We isolated SN-HLPf (Sambucus nigra hevein-like fruit protein), a hevein-like chitin-binding protein, from mature elderberry fruits. Cloning of the corresponding gene demonstrated that SN-HLPf is synthesized as a chimeric precursor consisting of an N-terminal chitin-binding domain corresponding to the mature elderberry protein and an unrelated C-terminal domain. Sequence comparisons indicated that the N-terminal domain of this precursor has high sequence similarity with the N-terminal domain of class I PR-4 (pathogenesis-related) proteins, whereas the C terminus is most closely related to that of class V chitinases. On the basis of these sequence homologies the gene encoding SN-HLPf can be considered a hybrid between a PR-4 and a class V chitinase gene.

Amino Acid Sequence↗

PubMed1998

Elderberry (Sambucus nigra) contains truncated Neu5Ac(alpha-2,6)Gal/GalNAc-binding type 2 ribosome-inactivating proteins.

Analysis of affinity-purified preparations of the fetuin-binding proteins from elderberry bark and fruits revealed besides the previously reported Neu5Ac(alpha-2,6)Gal/GalNAc-specific type 2 ribosome-inactivating proteins (RIP) the occurrence of single chain proteins of 22 kDa, which according to their N-terminal amino acid sequence correspond to the second part of the B chain of the respective type 2 RIP. Both proteins are very similar except that the polypeptides of the fruit lectin are 10 amino acid residues longer than these from the bark lectin. Our findings not only demonstrate the occurrence of carbohydrate-binding fragments of type 2 RIP but also provide further evidence that type 2 RIP genes give rise to complex mixtures of type 2 RIP/lectins in elderberry.

Acetylgalactosamine↗

PubMed1997

Osmotic stress activated expression of an Arabidopsis plasma membrane-associated protein: sequence and predicted secondary structure.

A cDNA clone At.MAMI (Arabidopsis thaliana membrane-associated mannitol-induced) was isolated from an Arabidopsis cDNA expression library by immunoselection. The cDNA was full-length (1.18 kb) with an open reading frame of 798 nucleotides encoding a 265 amino acid protein. The sequence of At.MAMI did not show any significant identity with other genes, as well as the deduced amino acid sequence with other proteins. However, prediction methods for the secondary structure of MAMI-30, together with homologous domains revealed some identity with VAP-33, a protein involved in membrane trafficking in neuronal tissues. In contrast to VAP-33, MAMI-30 did not exhibit a transmembrane domain, but positively charged loop regions could be involved in membrane anchoring. Indeed, MAMI-30 was immunodetected in purified plasma membrane from Arabidopsis cells. The gene was responsive to low turgor in Arabidopsis and its expression regulated developmentally. In addition, reduction of turgor caused a higher accumulation of mRNAs.

Amino Acid Sequence↗

PubMed1997

Type 1 ribosome-inactivating proteins are the most abundant proteins in iris (Iris hollandica var. Professor Blaauw) bulbs: characterization and molecular cloning.

The most abundant protein of Iris bulbs has been identified as a type 1 ribosome-inactivating protein (RIP). Analysis of the purified proteins and molecular cloning of the corresponding cDNAs demonstrated that this type 1 RIP is a mixture of three isoforms that exhibit a high degree of sequence identity and have similar, though not identical, ribosome-inactivating and polynucleotide:adenosine glycosidase activities. The accumulation of large quantities of type 1 RIP in a vegetative storage organ suggests that this presumed defence-related protein also plays a role in the nitrogen-storage metabolism of the bulb.

Amino Acid Sequence↗

PubMed1997

Elderberry (Sambucus nigra) bark contains two structurally different Neu5Ac(alpha2,6)Gal/GalNAc-binding type 2 ribosome-inactivating proteins.

A second NeuAc(alpha2,6)Gal/GalNAc binding type 2 ribosome-inactivating protein (RIP), called SNAI' has been isolated from elderberry (Sambucus nigra) bark. SNAI' is a minor bark protein which closely resembles the previously described major Neu5Ac(alpha2,6)Gal/GalNAc binding type 2 RIP called SNAI with respect to its carbohydrate-binding specificity and ribosome-inactivating activity but has a different molecular structure. Molecular cloning revealed that the deduced amino acid sequence of SNAI' is highly similar to that of SNAI and that the difference in molecular structure between both proteins relies on a single cysteine residue present in the B chain of SNAI but absent from SNAI'. The isolation of SNAI' not only identifies a minor bark protein as a type 2 RIP but also further emphasizes the complexity of the type 2 RIP/lectin mixture present in the bark of elderberry.

Amino Acid Sequence↗

PubMed1997

Isolation and molecular cloning of a novel type 2 ribosome-inactivating protein with an inactive B chain from elderberry (Sambucus nigra) bark.

One of the predominant proteins in the bark of elderberry (Sambucus nigra) has been identified as a novel type 2 ribosome-inactivating protein that exhibits a normal RNA N-glycosidase activity, but is devoid of carbohydrate binding activity. Sequence analysis of the corresponding cDNA clones revealed a striking homology to the previously cloned bark lectins from elderberry, suggesting that the new protein is a lectin-related protein. Molecular modeling of the protein confirmed that its A chain is fully active, whereas its B chain contains two functionally inactive carbohydrate-binding sites. These findings not only demonstrate for the first time the occurrence of a type 2 ribosome-inactivating protein with an inactive B chain, but also offer interesting perspectives for the synthesis of immunotoxins with an improved selectivity.

Amino Acid Sequence↗

PubMed1997

Curculin, a sweet-tasting and taste-modifying protein, is a non-functional mannose-binding lectin.

A three-dimensional model of curculin, a sweet-tasting and taste-modifying protein from the fruits of Curculigo latifolia, was built from the X-ray coordinates of GNA, a mannose-binding lectin from snowdrop (Galanthus nivalis). The three mannose-binding sites present in GNA were found in curculin but are devoid of mannose-binding activity as shown by docking experiments performed with mannose. Some regions well exposed on the surface of the three-dimensional model of curculin could act as epitopes responsible for the sweet-tasting properties of this protein.

Amino Acid Sequence↗

PubMed1997

Isolation, characterization and molecular cloning of the mannose-binding lectins from leaves and roots of garlic (Allium sativum L.).

Two novel lectins were isolated from roots and leaves of garlic. Characterization of the purified proteins indicated that the leaf lectin ASAL is a dimer of two identical subunits of 12 kDa, which closely resembles the leaf lectins from onion, leek and shallot with respect to its molecular structure and agglutination activity. In contrast, the root lectin ASARI, which is a dimer of subunits of 15 kDa, strongly differs from the leaf lectin with respect to its agglutination activity. cDNA cloning of the leaf and root lectins revealed that the deduced amino acid sequences of ASAL and ASARI are virtually identical. Since both lectins have identical N-terminal sequences the larger Mr of the ASARI subunits implies that the root lectin has an extra sequence at its C-terminus. These results not only demonstrate that virtually identical precursor polypeptides are differently processed at their C-terminus in roots and leaves but also indicate that differential processing yields mature lectins with strongly different biological activities. Further screening of the cDNA library for garlic roots also yielded a cDNA clone encoding a protein composed of two tandemly arrayed lectin domains. Since the presumed two-domain root lectin has not been isolated yet, its possible relationship to the previously described two-domain bulb lectin could not be studied at the protein level.

Amino Acid Sequence↗

PubMed1997

Molecular cloning of the bark and seed lectins from the Japanese pagoda tree (Sophora japonica).

cDNA clones encoding the bark and seed lectins from Sophora japonica were isolated and their sequences analyzed. Screening of a cDNA library constructed from polyA RNA isolated from the bark resulted in the isolation of three different lectin cDNA clones. The first clone encodes the GalNAc-specific bark lectin which was originally described by Hankins et al. [9] whereas the other clones encode the two isoforms of the mannose/glucose-specific lectin reported by Ueno et al. [34]. Molecular cloning of the seed lectin genes revealed that Sophora seeds contain only a GalNAc-specific lectin which is highly homologous to though not identical with the GalNAc-specific lectin from the bark. All lectin polypeptides are translated from mRNAs of ca. 1.3 kb encoding a precursor carrying a signal peptide. In the case of the mannose/glucose-specific bark lectins this precursor is post-translationally processed in two smaller peptides. Alignment of the deduced amino acid sequences of the different clones revealed striking sequence similarities between the mannose/glucose-binding and the GalNAc-specific lectins. Furthermore, there was a high degree of sequence homology with other legume lectins which allowed molecular modelling of the Sophora lectins using the coordinates of the Pisum sativum, Lathyrus ochrus and Erythrina corallodendron lectins.

Acetylgalactosamine↗

PubMed1997

The major elderberry (Sambucus nigra) fruit protein is a lectin derived from a truncated type 2 ribosome-inactivating protein.

The major protein of elderberry (Sambucus nigra L.) fruits is a lectin, called Sambucus nigra agglutinin IVf or SNAIVf. This lectin is composed of subunits that strongly resemble the B chain of the type 2 ribosome-inactivating protein (RIP), called SNAVf, present in the same tissue. To corroborate the possible relationship between both proteins their corresponding cDNAs were cloned and compared. Alignment of the deduced amino acid sequences revealed that the cDNA encoding SNAIVf is almost identical to that of SNAVf except that its A chain is truncated. Northern blot analysis confirmed that the mRNA encoding SNAIVf is about 500 nucleotides shorter than the SNAVf mRNA. In addition, the occurrence of a truncated type 2 RIP gene was unambiguously demonstrated by the analysis of PCR amplified genomic sequences. These results not only demonstrate for the first time that a plant lectin is encoded by a truncated type 2 RIP gene but also address important questions with respect to the molecular evolution of RIP and lectins.

Amino Acid Sequence↗

PubMed1996

Molecular cloning of the mitogenic mannose/maltose-specific rhizome lectin from Calystegia sepium.

cDNA clones encoding the mitogenic mannose/maltose-specific lectin from the rhizomes of hedge bindweed (Calystegia sepium) have been isolated and sequenced. Comparison of the deduced amino acid sequence and the molecular weight of the lectin subunit as determined by mass spectrometry indicated that the mature protein comprises the entire open reading frame of the cDNA, which implies that the primary translation product contains no signal peptide and is not proteolytically processed. Searches in the databases revealed sequence homology with the previously described lectins from the taxonomically unrelated Moraceae species Artocarpus integrifolia and Maclura pomifera.

Amino Acid Sequence↗

PubMed1996

Characterization and molecular cloning of Sambucus nigra agglutinin V (nigrin b), a GalNAc-specific type-2 ribosome-inactivating protein from the bark of elderberry (Sambucus nigra).

The molecular structure of the Sambucus nigra agglutinin V (SNAV), which has been described previously as a type-2 ribosome-inactivating protein called nigrin b, has been studied in detail by analysis of the purified protein combined with cDNA cloning and molecular modelling. Native SNAV is a dimer of two [A-s-s-B] pairs. Hapten inhibition assays indicated that GalNAc is a 20-fold more potent inhibitor of SNAV than Gal. A cDNA clone encoding SNAV was isolated from a cDNA library constructed with mRNA from the bark. Sequence analysis of this cDNA revealed a striking similarity to the recently cloned NeuAc alpha-2,6-gal/GalNAc-specific S. nigra bark agglutinin I (SNAI) and to the previously sequenced type-2 ribosome-inactivating proteins from Ricinus communis and Abrus precatorius. In addition, molecular modelling of SNAV further suggested that its structure closely resembles that of ricin. The N-terminal sequence of the B chain of SNAV also shows a marked similarity with the polypeptide of the previously described GalNAc-specific s. nigra bark agglutinin II (SNAII), which unlike SNAV and SNAI has no ribosome-inactivating activity. It appears, therefore, that elderberry bark contains at least two different type-2 ribosome-inactivating proteins and a lectin built up of subunits which are closely related to the B chain of SNAV.

Amino Acid Sequence↗

PubMed1996

The NeuAc(alpha-2,6)-Gal/GalNAc-binding lectin from elderberry (Sambucus nigra) bark, a type-2 ribosome-inactivating protein with an unusual specificity and structure.

The cDNA encoding the NeuAc(alpha-2,6)Gal/GalNAc binding lectin from elderberry (Sambucus nigra) bark (SNAI) was isolated from a cDNA library constructed with mRNA from the bark. Sequence analysis of this lectin cDNA revealed a striking similarity to the previously sequenced type-2 ribosome-inactivating proteins from Ricinus communis and Abrus precatorius. Molecular modelling of SNAI further indicated that its structure closely resembles that of ricin. Since SNAI strongly inhibits cell-free protein synthesis in a rabbit reticulocyte lysate it presumably is a type-2 ribosome-inactivating protein. However, SNAI differs from all previously described type-2 ribosome-inactivating proteins by its specificity towards NeuAc(alpha-2,6)Gal/GalNAc and its unusual molecular structure.

Amino Acid Sequence↗

PubMed1996

Molecular cloning of the lectin and a lectin-related protein from common Solomon's seal (Polygonatum multiflorum).

The most prominent protein of Polygonatum multiflorum (common Solomon's seal) rhizomes has been identified as a mannose-binding lectin. Analysis of the purified lectin demonstrated that it is a tetramer of four identical subunits of 14 kDa. Molecular cloning further revealed that the lectin from this typical Liliaceae species belongs to the superfamily of monocot mannose-binding proteins. Screening of cDNA libraries constructed with RNA isolated from buds, leaves and flowers of P. multiflorum also yielded cDNA clones encoding a protein, which contains two tandemly arranged domains with an obvious sequence homology to the mannose-binding lectins. Molecular modelling of the Polygonatum lectin and lectin-related protein indicated that the three-dimensional structure of both proteins strongly resembles that of the snowdrop lectin. In addition, this approach suggested that the presumed carbohydrate-binding sites of the lectin can accommodate a mannose residue whereas most of the carbohydrate-binding sites of the lectin-related protein cannot.

Amino Acid Sequence↗