Synthetic Cellular Chemistry Laboratory, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan.
J Am Chem Soc. 2011 Nov 2;133(43):17485-93. doi: 10.1021/ja207816h. Epub 2011 Oct 6.
Pradimicin A (PRM-A) is an actinomycete-derived antibiotic with the lectin-like property of being able to recognize D-mannopyranoside (Man) in the presence of Ca(2+) ion. PRM-A and its derivatives have been attracting a great deal of attention as the only family of natural carbohydrate receptors with nonpeptidic skeleton and, more recently, as conceptually novel drug candidates for human immunodeficiency virus (HIV). Despite its scientific interest and potential therapeutic importance, understanding how PRM-A recognizes Man has been severely limited. Conventional interaction analysis of PRM-A with Man in solution has been frustrated by aggregation of PRM-A and the three-component equilibrium consisting of the [PRM-A(2)/Ca(2+)], [PRM-A(2)/Ca(2+)/Man(2)], [PRM-A(2)/Ca(2+)/Man(4)] complexes, and their mixed oligomers. In this Article, we demonstrate the interaction analysis of PRM-A with methyl α-D-mannopyranoside (Man-OMe) in the solid state, which benefits from aggregate-forming propensity of PRM-A and eliminates the problem associated with the complicated equilibrium in solution. Isothermal titration calorimetry (ITC) analysis and coprecipitation experiments revealed that the primary Man binding of PRM-A is markedly tighter than the secondary one, leading to preparation of the solid aggregate solely composed of the [PRM-A(2)/Ca(2+)/Man-OMe(2)] complex. The simple 1:1 complexes of biosynthetically (13)C-enriched PRM-As and [(13)C(6)]Man-OMe facilitated the analysis of the primary Man binding of PRM-A by two-dimensional dipolar-assisted rotational resonance (2D-DARR), which clearly identified that the cavity consisted of D-alanine moiety and ABC rings of PRM-A is the Man binding site. Interestingly, the proposed Man binding site of PRM-A seems to resemble the typical architecture of artificial carbohydrate receptors.
普拉地霉素 A（PRM-A）是一种放线菌来源的抗生素，具有与钙离子结合时能够识别 D-甘露吡喃糖苷（Man）的凝集素样性质。PRM-A 及其衍生物因其非肽骨架的唯一天然碳水化合物受体家族而备受关注，最近因其作为人类免疫缺陷病毒（HIV）的概念新颖的候选药物而备受关注。尽管它具有科学意义和潜在的治疗重要性，但对 PRM-A 识别 Man 的机制了解甚少。PRM-A 与 Man 在溶液中的常规相互作用分析受到 PRM-A 聚集以及由 [PRM-A(2)/Ca(2+)],[PRM-A(2)/Ca(2+)/Man(2)],[PRM-A(2)/Ca(2+)/Man(4)]配合物及其混合低聚物组成的三组分平衡的限制。在本文中，我们展示了 PRM-A 与甲基 α-D-甘露吡喃糖苷（Man-OMe）在固态下的相互作用分析，这得益于 PRM-A 的聚集倾向，并解决了与溶液中复杂平衡相关的问题。等温滴定量热法（ITC）分析和共沉淀实验表明，PRM-A 与 Man 的主要结合明显比次要结合更紧密，导致仅由 [PRM-A(2)/Ca(2+)/Man-OMe(2)]配合物组成的固体聚集体的形成。生物合成（13）C 标记的 PRM-As 和 [(13)C(6)]Man-OMe 的简单 1:1 配合物促进了二维偶极辅助旋转共振（2D-DARR）对 PRM-A 与 Man 主要结合的分析，清楚地表明该空腔由 PRM-A 的 D-丙氨酸部分和 ABC 环组成，是 Man 的结合部位。有趣的是，PRM-A 的拟议 Man 结合部位似乎类似于典型的人工碳水化合物受体结构。
