Structural highlights
Publication Abstract from PubMedCEL-IV is a C-type lectin isolated from a sea cucumber, Cucumaria echinata. This lectin is composed of four identical C-type carbohydrate-recognition domains (CRDs). X-ray crystallographic analysis of CEL-IV revealed that its tetrameric structure was stabilized by multiple interchain disulfide bonds among the subunits. Although CEL-IV has the EPN motif in its carbohydrate-binding sites, which is known to be characteristic of mannose-binding C-type CRDs, it showed preferential binding of galactose and N-acetylgalactosamine. Structural analyses of CEL-IV/melibiose and CEL-IV/raffinose complexes revealed that their galactose residues were recognized in an inverted orientation compared with mannose-binding C-type CRDs containing the EPN motif, by the aid of a stacking interaction with the side chain of Trp79. Changes in the environment of Trp79 induced by binding to galactose were detected by changes in the intrinsic fluorescence and UV-absorption spectra of WT CEL-IV and its site-directed mutants. The binding specificity of CEL-IV toward complex oligosaccharides was analyzed by frontal affinity chromatography using various pyridylamino-sugars, and the results indicated preferential binding to oligosaccharides containing Galbeta1-3/4(Fucalpha1-3/4)GlcNAc structures. These findings suggest that the specificity for oligosaccharides may be largely affected by interactions with amino acid residues in the binding site other than those determining the monosaccharide-specificity. Galactose recognition by a tetrameric C-type lectin, CEL-IV, containing the EPN carbohydrate-recognition motif.,Hatakeyama T, Kamiya T, Kusunoki M, Nakamura-Tsuruta S, Hirabayashi J, Goda S, Unno H J Biol Chem. 2011 Jan 19. PMID:21247895[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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