Fushinobu Shinya
Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Acta Crystallogr F Struct Biol Commun. 2018 Aug 1;74(Pt 8):473-479. doi: 10.1107/S2053230X18006568. Epub 2018 Jul 26.
The lacto-N-biose I (Galβ1-3GlcNAc; LNB) disaccharide is present as a core unit of type-1 blood group antigens of animal glycoconjugates and milk oligosaccharides. Type-1 antigens often serve as cell-surface receptors for infection by pathogens. LNB in human milk oligosaccharides functions as a prebiotic for bifidobacteria and plays a key role in the symbiotic relationship of commensal gut microbes in infants. Protein Data Bank (PDB) entries exhibiting the LNB unit were investigated using the GlycoMapsDB web tool. There are currently 159 β-LNB and nine α-LNB moieties represented in ligands in the database. β-LNB and α-LNB moieties occur in 74 and six PDB entries, respectively, as NCS copies. The protein and enzyme structures are from various organisms including humans (galectins), viruses (haemagglutinin and capsid proteins), a pathogenic fungus, a parasitic nematode and protist, pathogenic bacteria (adhesins) and a symbiotic bacterium (a solute-binding protein of an ABC transporter). The conformations of LNB-containing glycans in enzymes vary significantly according to their mechanism of substrate recognition and catalysis. Analysis of glycosidic bond conformations indicated that the binding modes are significantly different in proteins adapted for modified or unmodified glycans.
乳糖-N-二糖I（Galβ1-3GlcNAc；LNB）二糖作为动物糖缀合物和乳寡糖1型血型抗原的核心单元存在。1型抗原常作为病原体感染的细胞表面受体。人乳寡糖中的LNB作为双歧杆菌的益生元，在婴儿共生肠道微生物的共生关系中起关键作用。使用GlycoMapsDB网络工具对展示LNB单元的蛋白质数据库（PDB）条目进行了研究。目前数据库中的配体中有159个β-LNB和9个α-LNB部分。β-LNB和α-LNB部分分别以NCS拷贝形式出现在74个和6个PDB条目中。蛋白质和酶结构来自包括人类（半乳糖凝集素）、病毒（血凝素和衣壳蛋白）、致病真菌、寄生线虫和原生生物、致病细菌（粘附素）以及共生细菌（ABC转运蛋白的溶质结合蛋白）在内的各种生物体。酶中含LNB聚糖的构象根据其底物识别和催化机制有很大差异。糖苷键构象分析表明，在适应修饰或未修饰聚糖的蛋白质中，结合模式有显著不同。
