Ternatin-family cyclic peptides inhibit protein synthesis by targeting the eukaryotic elongation factor-1α (eEF1A). A potentially related cytotoxic natural product (“A3”) was isolated from Aspergillus, but only 4 of its 11 stereocenters could be assigned. Here, we synthesized SR-A3 and SS-A3 – two out of 128 possible A3 epimers – and discovered that synthetic SR-A3 is indistinguishable from naturally derived A3. Relative to SS-A3, SR-A3 exhibits enhanced residence time and rebinding kinetics, as revealed by single-molecule fluorescence imaging of elongation reactions catalyzed by eEF1A in vitro. Increased residence time – stereospecifically conferred by the unique β-hydroxyl in SR-A3 – was also observed in cells. Consistent with its prolonged duration of action, thrice-weekly dosing with SR-A3 led to dramatically increased survival in an aggressive Myc-driven mouse lymphoma model. Our results demonstrate the potential of SR-A3 as a cancer therapeutic and exemplify an evolutionary mechanism for enhancing cyclic peptide binding kinetics via stereospecific side-chain hydroxylation.

中文翻译：

---

合成和单分子成像揭示了抗肿瘤 eEF1A 拮抗剂 SR-A3 对结合动力学的立体特异性增强

Ternatin 家族环肽通过靶向真核延伸因子-1α (eEF1A) 来抑制蛋白质合成。从曲霉中分离出一种可能相关的细胞毒性天然产物（“A3”），但只能确定其 11 个立体中心中的 4 个。在这里，我们合成了 SR-A3 和 SS-A3——128 种可能的 A3 差向异构体中的两种——并发现合成的 SR-A3 与天然衍生的 A3 没有区别。与 SS-A3 相比，SR-A3 表现出更长的停留时间和重新结合动力学，如 eEF1A 体外催化的延伸反应的单分子荧光成像所揭示的。在细胞中也观察到增加的停留时间——由 SR-A3 中独特的 β-羟基立体特异性地赋予。与其长期作用相一致，在侵袭性 Myc 驱动的小鼠淋巴瘤模型中，每周三次 SR-A3 给药可显着提高存活率。我们的结果证明了 SR-A3 作为癌症治疗剂的潜力，并举例说明了通过立体特异性侧链羟基化增强环肽结合动力学的进化机制。