Lectins from the Red Marine Algal Species Bryothamnion seaforthii and Bryothamnion triquetrum as Tools to Differentiate Human Colon Carcinoma Cells.

The carbohydrate-binding activity of the algal lectins from the closely related red marine algal species Bryothamnion triquetrum (BTL) and Bryothamnion seaforthii (BSL) was used to differentiate human colon carcinoma cell variants with respect to their cell membrane glyco-receptors. These lectins interacted with the cells tested in a dose-dependent manner. Moreover, the fluorescence spectra of both lectins clearly differentiated the cells used as shown by FACS profiles. Furthermore, as observed by confocal microscopy, BTL and BSL bound to cell surface glycoproteins underwent intense internalization, which makes them possible tools in targeting strategies.

Identification of a new quaternary association for legume lectins.

Lotus tetragonolobus lectin (LTA) is a fucose-specific legume lectin. Although several studies report a diverse combination of biological activities for LTA, little is known about the mechanisms involved in l-fucosyl oligosaccharide recognition. The crystal structure of LTA at 2.0A resolution reveals a different legume lectin tetramer. Its structure consists of a homotetramer composed of two back-to-back GS4-like dimers arranged in a new mode, resulting in a novel tetramer. The LTA N-linked carbohydrate at Asn4 and the unusual LTA dimer-dimer interaction are related to its particular mode of tetramerization. In addition, we used small angle X-ray scattering to investigate the quaternary structure of LTA in solution and to compare it to the crystalline structure. Although the crystal structure of LTA has revealed a conserved metal-binding site, its l-fucose-binding site presents some punctual differences. Our investigation of the new tetramer of LTA and its fucose-binding site is essential for further studies related to cross-linking between LTA and complex divalent l-fucosyl carbohydrates.

New crystal forms of Diocleinae lectins in the presence of different dimannosides.

Studying the interactions between lectins and sugars is important in order to explain the differences observed in the biological activities presented by the highly similar proteins of the Diocleinae subtribe. Here, the crystallization and preliminary X-ray data of Canavalia gladiata lectin (CGL) and C. maritima lectin (CML) complexed with Man(alpha1-2)Man(alpha1)OMe, Man(alpha1-3)Man(alpha1)OMe and Man(alpha1-4)Man(alpha1)OMe in two crystal forms [the complexes with Man(alpha1-3)Man(alpha1)OMe and Man(alpha1-4)Man(alpha1)OMe crystallized in space group P3(2) and those with Man(alpha1-2)Man(alpha1)OMe crystallized in space group I222], which differed from those of the native proteins (P2(1)2(1)2 for CML and C222 for CGL), are reported. The crystal complexes of ConA-like lectins with Man(alpha1-4)Man(alpha1)OMe are reported here for the first time.