Antitumor enediyne chromoprotein C-1027: Mechanistic investigation of the chromophore-mediated self-decomposition pathway
Antitumor enediyne chromoprotein C-1027: Mechanistic investigation of the chromophore-mediated self-decomposition pathway
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DOI：
10.1021/ja060724w
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发表时间：
2006-06-21
影响因子：
15
通讯作者：
Otani, Toshio
中科院分区：
文献类型：
--
作者：
Inoue, Masayuki;Usuki, Toyonobu;Otani, Toshio
C-1027是一种非常有效的抗肿瘤药物，可导致双链DNA断裂。它是一种独特的小分子-蛋白质复合物，由高活性的烯二炔发色团组成，通过自由基介导的氢提取与目标分子DNA结合，并通过载脂蛋白包裹发色团作为其载体到达DNA。虽然C-1027作为一种有效的药物递送系统具有良好的性能，但由于发色团对载脂蛋白的反应性，它的自分解速度很慢。了解C-1027是如何自我毁灭的，可以使其类似物的设计克服这一限制。本文描述了C-1027的自反应性，促进其自身分解的机理。我们提供的证据表明，促进氧化蛋白断裂和随后的发色团释放的Gly96自由基的形成是C-1027自分解的主要途径。根据新分离的自分解产物，我们提出载子蛋白有效地保护了对其生物活性至关重要的两个不同的发色团结构元件：九元烯二炔部分（DNA切割所必需的）和苯并恶嗪部分（DNA嵌入所必需的）。使用一种对发色团自由基更稳定的工程载脂蛋白类似物，我们表明天然C-1027在稳定性和抗肿瘤活性方面可以获得增强的整体性能。该结果是第一个合理设计的C-1027类似物，据报道其体外抗肿瘤活性优于天然C-1027。我们的发现可能对设计能够稳定封装高反应性小分子的蛋白质具有启示意义。
C-1027 is an extremely potent antitumor agent that causes double-stranded DNA cleavages. It is a unique small molecule-protein complex composed of a highly reactive enediyne chromophore, which upon binding reacts with its target molecule DNA through radical-mediated hydrogen abstraction and an apoprotein that encapsulates the chromophore serving as its carrier to reach DNA. Although C-1027 has favorable properties as an effective drug delivery system, it slowly self-decomposes due to the reactivity of the chromophore toward the apoprotein. Understanding how the C-1027 destroys itself may enable design of its analogues that overcome this limitation. In this paper, mechanistic insights into the self-reactivity of C-1027 that facilitates its own decomposition are described. We provide evidence that the formation of the Gly96 radical, which promotes the oxidative protein scission and the subsequent chromophore release, is the major pathway for the self-decomposition of C-1027. On the basis of the newly isolated products of the self-decomposition, we propose that the apoprotein effectively protects two different structural elements of the chromophore that are essential for its biological activity: the nine-membered enediyne moiety (necessary for DNA cleavage) and the benzoxazine moiety (necessary for DNA intercalation). Using an engineered apoprotein analogue kinetically more stable toward the chromophore radical, we show that enhanced overall properties can be achieved for the natural C-1027 with respect to stability and antitumor activities. The results present the first example of a rationally designed C-1027 analogue reported to display superior in vitro antitumor activity to the natural C-1027. Our findings may have implications for design of proteins that can stably encapsulate highly reactive small molecules.