Characterization of the Trimeric, Self‐Recognizing Geodia cydonium Lectin I

Abstract

A D-galactose-specific lectin I was extracted from the sponge Geodia cydonium and purified by affinity chromatography. The molecular weight of Iectin I as determined by high-pressure liquid gel chromatography, was found to be 36500 1300. Disc gel electrophoresis in the presence and in the absence of sodium dodecyl sulfate showed that lectin I is a trimer composed of three different subunits ( M , : 13 800,13 000 and 12200); two of the three subunits are linked by one disulfide bond. Isoelectric focusing gave a PI of 5.6 for the native molecule and a PI of 4.4 and of 7.4 for the subunits. The three subunits carry carbohydrate side chains, composed of D-galactose (94%) and of arabinose (5%). Based on experiments with lectins, the terminal i)-galactose residues are bound by p1+6 and/or fi1-4 glycosidic linkages. The Geodiu lectin I contains, besides two carbohydrate recognition sites, at least one receptor site for a second Iectin I molecule.Lectins are proteins (or glycoproteins) that bind carbohydrates and agglutinate cells; they have been isolated from viruses, bacteria and eukaryotes [l]. Since the initial work of Dodd et al. (21, a series of lectins have also been isolated from the oldest multicellular animals, the sponges [3 -61. In contrast to most other lectins, the biological role(s) of the sponge lectins are known to some extent. It has been demonstrated [7], that the D-galactose-specific lectin from Geodia cydoviium [5] is involved in the sorting-out of cells during reaggregation of allogeneic cells [S]. This lectin controls the activity of the cell membrane-associated antiaggregation receptor [9] by reversible binding to its D-galactose termini. This receptor, in its active state, has been shown to dissociate the complex, formed between the aggregation factor and the aggregation receptor [7, 81. In the xenogeneic system, using cells from the sponge Tethya lyncurium, the Geodia lectin causes cell agglutination [lo]. Later, evidence was presented suggesting that the lectin from Dictyostelium discoideum plays an analogous role in cellcell adhesion of cellular slime molds [II, 121. In previous reports on the properties of the Geodia lectin, two main aspects have been studied; firstly, the relationship between the hemagglutinin and the aggregation factor [5] and secondly, the mitogenic activity of the lectin for human lymphocytes [6]. In the present contribution a detailed physicochemical characterization of the Geodia lectin I (the main lectin in this sponge) is given, demonstrating that it is a trimer of a molecular weight of 36 500, with the property to react with D-galactose termini of its own protein species. These two characteristics have not yet been observed with other lectins. One lectin from rat liver membranes has been described [13], which binds to its own galactose residues after a pretreatment with neuraminidase. MATERIALS AND METHODS Lectin Extraction and PurificationThe siliceous sponge Geodia cydoniurn (Jam.) was collected near Rovinj (Mediterranean Sea) and the lectins were isolatedAhhrev...

Origin of metazoan adhesion molecules and adhesion receptors as deduced from cDNA analyses in the marine sponge Geodia cydonium : a review

“…The purified molecules have an M r of 13-18 kDa (Bretting et al 1981;Müller et al 1983) and bind specifically to the sugars DGalNAc, DGalß1 → 4DGlcNAc, DGal β1 → 3DGlcNAc and DGalNAc (Vaith et al 1979;Bretting et al 1981); the highest specificity has been determined for GalNAcα1-3GalNAc (Forssman disaccharide) and GalNAcα1-3(Fucα1-2)Gal (blood group A; Hanisch et al 1996). In the presence of Ca 2+ , sponge galectins undergo conformational changes and "polymerize" into large three-dimensional clumps (Diehl-Seifert et al 1985b;Fig.…”

Multi‐antennary Galβ1→4GlcNAc and Galβ1→3GalNAc clusters as important ligands for a lectin isolated from the sponge Geodia cydonium

“…cydonium [2, 3], has been sequenced on the protein and DNA levels and shown to exhibit striking homology to the carbohydrate recognition domain characteristic for mammalian galectin‐1 [2, 3]. The lectin molecule binds two moles of lactose per mole of native lectin in a calcium independent manner [4]. Recently, it was shown that GCL binds with high affinity for the blood group A trisaccharide and even more strongly for the Forssman di‐ and pentasaccharides [5].…”

A d-mannose-specific lectin from Gerardia savaglia that inhibits nucleocytoplasmic transport of mRNA

“…The determination of the relative molecular mass of the lectin by high-pressure liquid gel chromatography was performed essentially as described earlier [2]. The calibration curve of the molecular mass marker proteins was found to be linear after plotting the ratio between the retention times (tr) and the time for the pressure peak (to) against the logarithm of the M , of the calibration proteins (mentioned in the legend to Fig.…”

“…For the analysis of the sugar content in the purified lectin preparation a described procedure [2] was applied.…”