Malaria control is threatened by a limited pipeline of effective pharmaceuticals against drug-resistant strains of Plasmodium falciparum. Components of the mitochondrial electron transport chain (ETC) are attractive targets for drug development, owing to exploitable differences between the parasite and human ETC. Disruption of ETC function interferes with metabolic processes including de novo pyrimidine synthesis, essential for nucleic acid replication. We investigated the effects of ETC inhibitor selection on two distinct P. falciparum clones, Dd2 and 106/1. Compounds CK-2-68 and RYL-552, substituted quinolones reported to block P. falciparum NADH dehydrogenase 2 (PfNDH2; a type II NADH:quinone oxidoreductase), unexpectedly selected mutations at the quinol oxidation (Q_o) pocket of P. falciparum cytochrome B (PfCytB). Selection experiments with atovaquone (ATQ) on 106/1 parasites yielded highly resistant PfCytB Y268S mutants seen in clinical infections that fail ATQ-proguanil treatment. In contrast, ATQ pressure on Dd2 yielded moderately resistant parasites carrying a PfCytB M133I or K272R mutation. Strikingly, all ATQ-selected mutants demonstrated little change or slight increase of sensitivity to CK-2-68 or RYL-552. Molecular docking studies demonstrated binding of all three ETC inhibitors to the Q_o pocket of PfCytB, where Y268 forms strong van der Waals interactions with the hydroxynaphthoquinone ring of ATQ but not the quinolone ring of CK-2-68 or RYL-552. Our results suggest that combinations of suitable ETC inhibitors may be able to subvert or delay the development of P. falciparum drug resistance.

有限的有效药物渠道对恶性疟原虫的耐药菌株威胁着疟疾的控制。线粒体电子传输链（ETC）的组成部分是寄生虫和人类ETC之间可利用的差异，因此是药物开发的有吸引力的目标。ETC功能的破坏会干扰包括从头合成嘧啶的合成在内的代谢过程，这对于核酸复制是必不可少的。我们调查了ETC抑制剂选择对两个不同的恶性疟原虫克隆Dd2和106/1的影响。化合物CK-2-68和RYL-552，取代的喹诺酮类药物可阻断恶性疟原虫NADH脱氢酶2（PfNDH2； II型NADH：醌氧化还原酶），在恶性疟原虫细胞色素B（PfCytB）的喹诺酮氧化（Q _o）口袋中出乎意料地选择了突变。在106/1寄生虫上用atovaquone（ATQ）进行的选择实验产生了高耐药性PfCytB Y268S突变体，这种突变体在ATQ-proguanil治疗失败的临床感染中可见。相反，在Dd2上的ATQ压力产生带有PfCytB M133I或K272R突变的中等抵抗力的寄生虫。引人注目的是，所有ATQ选择的突变体对CK-2-68或RYL-552的敏感性几乎没有变化或仅略有增加。分子对接研究表明，所有三种ETC抑制剂均与Q _o结合。PfCytB的口袋，其中Y268与ATQ的羟基萘醌环形成强范德华相互作用，而与CK-2-68或RYL-552的喹诺酮环不形成强范德华相互作用。我们的结果表明，合适的ETC抑制剂的组合可能能够颠覆或延迟恶性疟原虫耐药性的发展。