Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Acc Chem Res. 2013 Jul 16;46(7):1567-78. doi: 10.1021/ar300315p. Epub 2013 Mar 14.
Polytheonamide B (1), isolated from the marine sponge Theonella swinhoei, is a posttranslationally modified ribosomal peptide (MW 5030 Da) that displays extraordinary cytotoxicity. Among its 48 amino acid residues, this peptide includes a variety D- and L-amino acids that do not occur in proteins, and the chiralities of these amino acids alternate in sequence. These structural features induce the formation of a stable β6.3-helix, giving rise to a tubular structure of over 4 nm in length. In the biological setting, this fold is believed to transport cations across the lipid bilayer through a pore, thereby acting as an ion channel. In this Account, we discuss the construction and structural permutations of this potent cytotoxin. First we describe the 161-step chemical construction of this unusual peptide 1. By developing a synthetic route to 1, we established the chemical basis for subsequent SAR studies to pinpoint the proteinogenic and nonproteinogenic building blocks within the molecule that confer its toxicity and channel function. Using fully synthetic 1, we generated seven analogues with point mutations, and studies of their activity revealed the importance of the N-terminal moiety. Next, we simplified the structure of 1 by substituting six amino acid residues of 1 to design a more synthetically accessible analogue 9. This dansylated polytheonamide mimic 9 was synthesized in 127 total steps, and we evaluated its function to show that it can emulate the toxic and ion channel activities of 1 despite its multiple structural modifications. Finally, we applied a highly automated synthetic route to 48-mer 9 to generate 13 substructures of 27-39-mers. The 37-mer 12 exhibited nanomolar level toxicity through a potentially distinct mode of action from 1 and 9. The SAR studies of polytheonamide B and the 21 artificial analogues have deepened our understanding of the precise structural requirements for the biological functions of 1. They have also led to the discovery of artificial molecules with various toxicities and channel functions. These achievements demonstrate the benefits of total synthesis and the importance of efficient construction of complex molecules. The knowledge accumulated through these studies will be useful for the rational design of new tailor-made channel peptides and cytotoxic molecules with desired functions.
聚醚酰胺 B（1）是从海绵 Theonella swinhoei 中分离出来的一种翻译后修饰核糖体肽（MW 5030 Da），具有非凡的细胞毒性。在其 48 个氨基酸残基中，该肽包含多种在蛋白质中不存在的 D-和 L-氨基酸，并且这些氨基酸的手性在序列中交替。这些结构特征诱导形成稳定的β6.3-螺旋，从而产生长度超过 4nm 的管状结构。在生物环境中，这种折叠结构被认为是通过孔道将阳离子运输穿过脂双层，从而充当离子通道。在本报告中，我们讨论了这种强效细胞毒素的构建和结构变化。首先，我们描述了这种不寻常肽 1 的 161 步化学构建。通过开发该分子的合成途径，我们为后续的 SAR 研究奠定了化学基础，以确定分子中赋予其毒性和通道功能的蛋白质和非蛋白质构建块。使用全合成的 1，我们生成了七个带有点突变的类似物，并对其活性研究表明 N 端部分的重要性。接下来，我们通过取代 1 的六个氨基酸残基来简化 1 的结构，设计了一种更具合成可及性的类似物 9。该丹磺酰聚醚酰胺模拟物 9 经 127 步总合成，我们评估了其功能，表明尽管结构修饰较多，但它可以模拟 1 的毒性和离子通道活性。最后，我们应用高度自动化的合成途径合成 48 聚体 9，生成了 27-39 聚体的 13 个亚结构。37 聚体 12 通过可能与 1 和 9 不同的作用模式表现出纳摩尔级别的毒性。对聚醚酰胺 B 和 21 个人工类似物的 SAR 研究加深了我们对 1 生物功能的精确结构要求的理解。它们还导致发现了具有各种毒性和通道功能的人工分子。这些成就证明了全合成的益处和高效构建复杂分子的重要性。通过这些研究积累的知识将有助于理性设计具有所需功能的新型定制通道肽和细胞毒性分子。
