The small molecule IACS-010759 has been reported to potently inhibit the proliferation of glycolysis-deficient hypoxic tumor cells by interfering with the functions of mitochondrial NADH-ubiquinone oxidoreductase (complex I) without exhibiting cytotoxicity at tolerated doses in normal cells. Considering the significant cytotoxicity of conventional quinone-site inhibitors of complex I, such as piericidin and acetogenin families, we hypothesized that the mechanism of action of IACS-010759 on complex I differs from that of other known quinone-site inhibitors. To test this possibility, here we investigated IACS-010759's mechanism in bovine heart submitochondrial particles. We found that IACS-010759, like known quinone-site inhibitors, suppresses chemical modification by the tosyl reagent AL1 of Asp160 in the 49-kDa subunit, located deep in the interior of a previously proposed quinone-access channel. However, contrary to the other inhibitors, IACS-010759 direction-dependently inhibited forward and reverse electron transfer and did not suppress binding of the quinazoline-type inhibitor [125I]AzQ to the N terminus of the 49-kDa subunit. Photoaffinity labeling experiments revealed that the photoreactive derivative [125I]IACS-010759-PD1 binds to the middle of the membrane subunit ND1 and that inhibitors that bind to the 49-kDa or PSST subunit cannot suppress the binding. We conclude that IACS-010759's binding location in complex I differs from that of any other known inhibitor of the enzyme. Our findings, along with those from previous study, reveal that the mechanisms of action of complex I inhibitors with widely different chemical properties are more diverse than can be accounted for by the quinone-access channel model proposed by structural biology studies.

中文翻译：

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IACS-010759 是一种糖酵解缺陷型缺氧肿瘤细胞的有效抑制剂，通过独特的机制抑制线粒体呼吸复合物 I。


据报道，小分子 IACS-010759 通过干扰线粒体 NADH-泛醌氧化还原酶（复合物 I）的功能，有效抑制糖酵解缺陷的缺氧肿瘤细胞的增殖，并且在正常细胞的耐受剂量下不会表现出细胞毒性。考虑到复合物 I 的常规醌位点抑制剂（例如杀粉粉素和乙酰丙酮家族）具有显着的细胞毒性，我们假设 IACS-010759 对复合物 I 的作用机制不同于其他已知的醌位点抑制剂。为了测试这种可能性，我们在这里研究了 IACS-010759 在牛心脏软骨下颗粒中的机制。我们发现，IACS-010759 与已知的醌位点抑制剂一样，可抑制 49-kDa 亚基中 Asp160 的甲苯磺酰基试剂 AL1 的化学修饰，该亚基位于先前提出的醌通道内部深处。然而，与其他抑制剂相反，IACS-010759 方向依赖性地抑制正向和反向电子转移，并且不抑制喹唑啉型抑制剂 [125I]AzQ 与 49-kDa 亚基 N 末端的结合。光亲和标记实验表明，光反应衍生物 [125I]IACS-010759-PD1 与膜亚基 ND1 的中部结合，而与 49-kDa 或 PSST 亚基结合的抑制剂不能抑制这种结合。我们得出结论，IACS-010759 在复合物 I 中的结合位置不同于任何其他已知的酶抑制剂。我们的研究结果以及之前的研究结果表明，具有广泛不同化学性质的复合物 I 抑制剂的作用机制比结构生物学研究提出的醌通道模型所能解释的更加多样化。