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首页> 外文期刊>Journal of Molecular Biology >Crystal Structure of the Jacalin-T-antigen Complex and a Comparative Study of Lectin-T-antigen Complexes.
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Crystal Structure of the Jacalin-T-antigen Complex and a Comparative Study of Lectin-T-antigen Complexes.

机译：Jacalin-T-抗原复合物的晶体结构和凝集素-T-抗原复合物的比较研究。

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摘要

Thomsen-Friedenreich antigen (Galbeta1-3GalNAc), generally known as T-antigen, is expressed in more than 85% of human carcinomas. Therefore, proteins which specifically bind T-antigen have potential diagnostic value. Jacalin, a lectin from jack fruit (Artocarpus integrifolia) seeds, is a tetramer of molecular mass 66kDa. It is one of the very few proteins which are known to bind T-antigen. The crystal structure of the jacalin-T-antigen complex has been determined at 1.62A resolution. The interactions of the disaccharide at the binding site are predominantly through the GalNAc moiety, with Gal interacting only through water molecules. They include a hydrogen bond between the anomeric oxygen of GalNAc and the pi electrons of an aromatic side-chain. Several intermolecular interactions involving the bound carbohydrate contribute to the stability of the crystal structure. The present structure, along with that of the Me-alpha-Gal complex, provides a reasonable qualitative explanation for the known affinities of jacalin to different carbohydrate ligands and a plausible model of the binding of the lectin to T-antigen O-linked to seryl or threonyl residues. Including the present one, the structures of five lectin-T-antigen complexes are available. GalNAc occupies the primary binding site in three of them, while Gal occupies the site in two. The choice appears to be related to the ability of the lectin to bind sialylated sugars. In either case, most of the lectin-disaccharide interactions are at the primary binding site. The conformation of T-antigen in the five complexes is nearly the same.
机译：Thomsen-Friedenreich抗原（Galbeta1-3GalNAc），通常称为T抗原，在超过85％的人类癌症中表达。因此，特异性结合T抗原的蛋白质具有潜在的诊断价值。 Jacalin是一种来自杰克果（Artocarpus integrifolia）种子的凝集素，是分子量为66kDa的四聚体。它是已知结合T抗原的极少数蛋白质之一。贾卡林-T-抗原复合物的晶体结构已在1.62A分辨率下确定。二糖在结合位点的相互作用主要通过GalNAc部分，而Gal仅通过水分子相互作用。它们在GalNAc的异头氧与芳族侧链的pi电子之间包含氢键。涉及结合的碳水化合物的几种分子间相互作用有助于晶体结构的稳定性。本结构以及Me-alpha-Gal复合物的结构为已知的jacalin与不同碳水化合物配体的亲和力以及凝集素与T-抗原O-连接到丝氨酸的结合的合理模型提供了合理的定性解释。或苏糖基残基。包括本发明在内，可获得五种凝集素-T-抗原复合物的结构。 GalNAc在其中三个中占据主要结合位点，而Gal在两个中占据主要结合位点。选择似乎与凝集素结合唾液酸化糖的能力有关。无论哪种情况，大多数凝集素-二糖相互作用都在主要结合位点处。这五个复合物中T抗原的构象几乎相同。

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