Fucose-binding Lectins

This fairly straightforward concept of the stereochemical features defining the specificity of eel serum was, however, complicated by an unexpected finding extremely low concentrations (for example, 0.3 /Ag/ml) of an L-fucose-free polysaccharide from Taxus cuspidata com- 

Eel Serum-O Erythrocyte Agglutination and Eel Serum-H(O) Substance Precipitation Sugar Inhibition Studies167,674,67  

Sugar Minimum amount completely inhibiting 4 hemagglutinating doses (mg/ml) Amount giving 50% inhibition of precipitation (junoles) 

Another feature of the eel-serum specificity that is unlike that of other lectins is the existence of anomeric preference only within the L-fucose series.167,674 Thus, a-L-fucopyranosides are two to five times as efficient as inhibitors as their parent compounds, whereas their /3-L-glycosidically linked counterparts have half to one-third the effect. On the other hand, the anomers of methyl 3-O-methyl-D-fucopyranoside are of equivalent activity, being approximately twice as active as the parent saccharide. In the D series, over 90% of the binding energy is evidently accounted for by parts of the sugar molecule other than the anomeric carbon atom and the aglycon. 

Springer and coworkers874 reported an extensive list of saccharides that were weakly inhibiting or noninhibiting. These included the 2-acetamido-2-deoxy derivatives of D-galactose, D-glucose, D-ribose, D-talose, and D-arabinose, 3,6-dideoxy-L- and -D-xy/o-hexose, L-lyxo-hexosulose, L-arabinose, D-fructose, and 2-deoxy-D-erythro-pentose. 

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Figure 4. Pea stem material was sequentially extracted with hot 70% ethanol, 0.1 M EDTA and 4% KOH-0.1% NaBH4 to leave xyloglucan-cellulose cell wall ghosts . Binding of fluorescent fucose-binding lectin from Ulex europeus as visualized by fluorescence microscopy shows xyloglucan distributed over the whole wall surface. Photograph courtesy of Dr. T. Hayashi.

O-methylation on the basis of structural similarities between D- and L-fucose derivatives as noted in three-dimensional models. Thus, a similarity in profile and in regions of low hydrogen-bonding capability is evident between 2-O-methyl-D-fucose and L-fucose, if the latter is rotated 180° about its horizontal axis. This phenomenon is even more apparent in the binding of D-fucose derivatives to the L-fucose-binding lectin of the eel167 (see Section VI,1). 

Ulex eurnpaeus II (gorse see also L-fucose-binding lectins)... 

Ulex europaeus seeds contain two agglutinins an L-fucose-binding lectin (U. europaeus I, UFA I) and U. europaeus II (UEA II), which is most potently Inhibited by V-acetylated chitodextrins and L-Fuc(al-2)Gal( 3l-4)GlcNAc. 

UEA I has been sequenced and shown to exhibit extensive homology with many other legume lectins, but not with Lotus tetragonolobus, another L-fucose-binding lectin. 

Highly porous and hydrophilic supports have been prepared by co-polymerization of A-tris(hydroxymethyl)methyl acrylamide or A-tris(hydroxymethyl)-methyl methacrylamide with acrylic monomers bearing carboxyl functions, and then treated with 4-aminophenyl a-L-fucoside using a water-soluble carbodi-imide mediator. The support was used for purification of the L-fucose-binding lectin from Ulex europeus. 

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