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Biomedical subjects

H M Stinissen

Publications and source records attributed to H M Stinissen.

8 recordsLinked to original sources
PubMed1985

A new type of cereal lectin from leaves of couch grass (Agropyrum repens).

Extracts from couch grass (Agropyrum repens) leaves contain relatively high lectin concentrations. Preliminary experiments with crude extracts indicated that the leaf lectin differs from the embryo lectin of the same species and other Gramineae embryo lectins with respect to its sugar and blood group specificity, and serological properties. A comparison of the biochemical, physicochemical and biological properties of purified lectins from couch grass leaves and embryos, and wheat germ agglutinin revealed that the leaf lectin has the same molecular structure as the embryo lectins. It is a dimer composed of two identical subunits, which, however, are slightly larger than embryo lectin subunits. Structural differences between both couch grass lectins were further inferred from in vitro subunit exchange experiments and serological analyses. Whereas the embryo lectin readily forms heterodimers with embryo lectins from other cereal species and also is serologically indistinguishable from them, the leaf lectin does not exchange subunits with the same embryo lectins and is serologically different. In addition, couch grass leaf lectin exhibits specificity for N-acetylgalactosamine and agglutinates preferentially blood-group-A erythrocytes whereas the embryo lectin is not inhibited by N-acetylgalactosamine and exhibits no blood-group specificity. It was observed also that the lectin content of couch grass leaves varies enormously during the seasons.

Amino Acids↗
PubMed1985

Posttranslational processing of proteins in vacuoles and protein bodies is inhibited by monensin.

A number of proteins that accumulate in vacuoles and protein bodies undergo posttranslational processing at these accumulation sites. These processing steps include proteolytic cleavage (e.g. pea lectin, soybean glycinin, and rice lectin) and the removal of some sugar residues from oligosaccharide side-chains (e.g. bean phytohemagglutinin). Treatment of immature rice embryos with the sodium ionophore monensin slows down the proteolytic processing of the rice lectin precursor (M(r) 23,000) to mature rice lectin (M(r) 10,000 and 8,000). Treatment of developing bean cotyledons with monensin slows down the removal of peripheral N-acetylglucosamine residues from the oligosaccharide side-chains of phytohemagglutinin. The results are consistent with the interpretation that these processing steps, which occur in vacuoles or protein bodies, are carried out by enzymes with an acidic pH optimum, and that monensin slows down processing by alkalinization of the vacuoles or protein bodies.

Journal Article↗
PubMed1985

Isolation and Partial Characterization of a New Lectin from Seeds of the Greater Celandine (Chelidonium majus).

Seeds of the greater celandine (Chelidonium majus L.) contain a lectin which could be isolated using a combination of affinity chromatography on chitin and ion exchange chromatography on sulphopropyl-Sephadex. The purified lectin was partially characterized with respect to its biochemical and physicochemical properties. It is a small dimeric protein composed of two different subunits of M(r) 9,500 and 11,500, respectively. Its amino acid composition is typified by high contents of glycine and cysteine. No covalently bound carbohydrate could be detected. Hapten inhibition experiments indicated that the lectin exhibits specificity towards oligomers of N-acetylglucosamine, the potency of inhibition increasing with chain length up to four residues. The greater celandine lectin is the first lectin to be isolated from a species belonging to the plant family Papaveraceae (poppy family). Although it represents a new type of plant lectin, resemblances to phytohemaglutinins from diverse taxonomic origin are obvious.

Journal Article↗
PubMed1985

Lectin in Vegetative Tissues of Adult Barley Plants Grown under Field Conditions.

A study of the distribution of lectins over different vegetative tissues of barley (Hordeum vulgare L.) plants, which were grown under normal crop conditions, indicated that lectin occurs in roots, leaves, and developing ears. Isolation and characterization of both root and leaf lectins led to the conclusions (a) that they are indistinguishable from the embryo lectin and (b) that the total lectin content of these vegetative organs is many times higher than that of the embryo. Finally, in vivo labeling experiments demonstrated that the lectin is synthesized de novo in roots and leaves.

Journal Article↗
PubMed1984

Subcellular site of lectin synthesis in developing rice embryos.

Embryos of developing rice (Oryza sativa L. cv. Koshihikari) caryopses which actively synthesize lectin were labelled with [S]cysteine for different times and newly synthesized rice lectin was isolated by affinity chromatography. Gel filtration of embryo extracts on Sepharose-4B indicated that a large portion of the labelled lectin was associated with the particulate fraction. Experiments with detergent indicated that this lectin was sequestered within organelles. When extracts of pulse-labelled embryos were fractionated on isopycnic sucrose gradients, this detergent-released lectin banded in the same density-region as the endoplasmic reticulum (ER) marker enzyme NADH-cytochrome c reductase. Both radioactivity in rice lectin and the enzyme activity shifted towards a higher density in the presence of 2 mM Mg acetate, indicating that the labelled lectin was associated with the rough ER. The ER-bound lectin could be chased from this organelle when tissue was incubated in unlabelled cysteine following a 1 h pulse of labelled cysteine. Radioactivity chased out of the ER with a half-life of 4 h and accumulated in the soluble fraction. In the ER the lectin was present as a polypeptide with mol. wt. 23 000, while in the soluble fraction it occurred as polypeptides with mol. wt. 18 000, 10 000 and 8000. The rice lectin in the ER is capable of binding carbohydrates since it binds readily to the affinity gels. It is associated into dimers with an approximate mol. wt. of 46 000. The results show that newly synthesized rice lectin is transiently sequestered within the ER before further transport and processing take place.

Journal Article↗
PubMed1982

Isolation and partial characterization of a lectin from a false brome grass (Brachypodium sylvaticum).

A lectin has been isolated from embryos of a false brome grass species (Brachypodium sylvaticum) by affinity chromatography on immobilized N-acetylglucosamine. It is a dimeric protein of two identical subunits of mol.wt. 18 000. Although it resembles cereal lectins with respect to its biochemical and physicochemical properties, it differs structurally in several aspects from wheat-germ-agglutinin-like lectins.

Chromatography, Affinity↗
PubMed1982

Isolation and partial characterization of wheat-germ-agglutinin-like lectins from rye (Secale cereale) and barley (Hordeum vulgare) embryos.

Lectins have been isolated from embryos of Secale cereale (rye) and Hordeum vulgare (barley) by affinity chromatography on immobilized N-acetylglucosamine. Both lectins are dimeric proteins of two identical subunits of mol.wt. 18000. They resemble strongly wheat-germ agglutinin with respect to their chemical, physical, biological and immunological properties.

Amino Acids↗