Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA.
Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA; NIH Intramural Cryo-EM Consortium (NICE), Bethesda, Maryland, USA.
J Biol Chem. 2023 Jul;299(7):104860. doi: 10.1016/j.jbc.2023.104860. Epub 2023 May 24.
Among the various components of the protozoan Plasmodium mitochondrial respiratory chain, only Complex III is a validated cellular target for antimalarial drugs. The compound CK-2-68 was developed to specifically target the alternate NADH dehydrogenase of the malaria parasite respiratory chain, but the true target for its antimalarial activity has been controversial. Here, we report the cryo-EM structure of mammalian mitochondrial Complex III bound with CK-2-68 and examine the structure-function relationships of the inhibitor's selective action on Plasmodium. We show that CK-2-68 binds specifically to the quinol oxidation site of Complex III, arresting the motion of the iron-sulfur protein subunit, which suggests an inhibition mechanism similar to that of P-type Complex III inhibitors such as atovaquone, stigmatellin, and UHDBT. Our results shed light on the mechanisms of observed resistance conferred by mutations, elucidate the molecular basis of the wide therapeutic window of CK-2-68 for selective action of Plasmodium vs. host cytochrome bc, and provide guidance for future development of antimalarials targeting Complex III.
在原生动物疟原虫线粒体呼吸链的各种成分中，只有复合物 III 是已被证实的抗疟药物的细胞靶点。化合物 CK-2-68 的开发是为了专门针对疟原虫呼吸链的替代 NADH 脱氢酶，但它的抗疟活性的真正靶点一直存在争议。在这里，我们报告了与 CK-2-68 结合的哺乳动物线粒体复合物 III 的冷冻电镜结构，并研究了抑制剂对疟原虫选择性作用的结构-功能关系。我们表明，CK-2-68 特异性地结合到复合物 III 的醌氧化位点，阻止了铁硫蛋白亚基的运动，这表明其抑制机制类似于 P 型复合物 III 抑制剂，如阿托伐醌、stigmatellin 和 UHDBT。我们的结果阐明了观察到的突变赋予的耐药性机制，阐明了 CK-2-68 对疟原虫与宿主细胞色素 bc 选择性作用的宽治疗窗口的分子基础，并为针对复合物 III 的抗疟药物的未来开发提供了指导。
