title: Galectin-8-N-domain recognition mechanism for sialylated and sulfated glycans.
abstract: Galectin-8 has much higher affinity for 3'-O-sulfated or 3'-O-sialylated glycoconjugates and a Lewis X-containing glycan than for oligosaccharides terminating in Galβ1→3/4GlcNAc, and this specificity is mainly attributed to the N-terminal carbohydrate recognition domain (N-domain, CRD) (Ideo, H., Seko, A., Ishizuka, I., and Yamashita, K. (2003) Glycobiology 13, 713-723). In this study, we elucidated the crystal structures of the human galectin-8-N-domain (-8N) in the absence or presence of 4 ligands. The apo molecule forms a dimer, which is different from the canonical 2-fold symmetric dimer observed for galectin-1 and -2. In a galectin-8N-lactose complex, the lactose-recognizing amino acids are highly conserved among the galectins. However, Arg(45), Gln(47), Arg(59), and the long loop region between the S3 and S4 β-strands are unique to galectin-8N. These amino acids directly or indirectly interact with the sulfate or sialic acid moieties of 3'-sialyl- and 3'-sulfolactose complexed with galectin-8N. Furthermore, in the LNF-III-galectin-8N complex, van der Waals interactions occur between the α1-3-branched fucose and galactose and between galactose and Tyr(141), and these interactions increase the affinity toward galectin-8N. Based on the findings of these x-ray crystallographic analyses, a mutagenesis study using surface plasmon resonance showed that Arg(45), Gln(47), and Arg(59) of galectin-8N are indispensable and coordinately contribute to the strong binding of galectins-8N to sialylated and sulfated oligosaccharides. Arg(59) is the most critical amino acid for binding in the S3-S4 loop region.
authors.affiliation: Innovative Research Initiatives, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ideo
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Matsuzaka
authors.forename: Takamasa
authors.initials: T
authors.lastname: Nonaka
authors.forename: Akira
authors.initials: A
authors.lastname: Seko
authors.forename: Katsuko
authors.initials: K
authors.lastname: Yamashita
mesh_terms: D018360:Crystallography, X-Ray; D037161:Galectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007983:Lewis Blood Group Antigens; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance
chemical_list: D037161:Galectins; C091991:LGALS8 protein, human; D007983:Lewis Blood Group Antigens; C494219:Lewis a oligosaccharide; D009844:Oligosaccharides