Department of Biological Chemistry, College of Agriculture, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan.
Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University of Science, Maeda, Teine, Sapporo, Hokkaido 006-8585, Japan.
J Biochem. 2020 Oct 1;168(4):427-434. doi: 10.1093/jb/mvaa060.
The malaria parasite (Plasmodium sp.) contains a plastid-derived organelle called the apicoplast, which is essential for the growth of the parasite. In this organelle, a redox system comprising plant-type ferredoxin (Fd) and Fd: NADP(H) oxidoreductase (FNR) supplies reducing power for the crucial metabolic pathways. Electron transfer between Plasmodium falciparum Fd (PfFd) and FNR (PfFNR) is performed with higher affinity and specificity than those of plant Fd and FNR. We investigated the structural basis for such superior protein-protein interaction by focussing on the Plasumodium-specific regions of PfFd. Significant contribution of the C-terminal region of PfFd for the electron transfer with PfFNR was revealed by exchanging the C-terminal three residues between plant Fd and PfFd. Further site-directed mutagenesis of the PfFd C-terminal residues indicated that the presence of aromatic residue at Positions 96 and 97 contributes to the lower Km for PfFNR. Physical binding analyses using fluorescence and calorimetric measurements supported the results. A mutation from Asp to Tyr at position 97 of PfFd was recently reported to be strongly associated with P. falciparum resistance to artemisinin, the front line anti-malarial drug. Thus, the enhanced interaction of PfFd D97Y protein with PfFNR could be involved in artemisinin resistance of human malaria parasites.
疟原虫（Plasmodium sp.）含有一种质体衍生的细胞器，称为类质体，它对寄生虫的生长至关重要。在这个细胞器中，由植物型铁氧还蛋白（Fd）和 Fd：NADP（H）氧化还原酶（FNR）组成的氧化还原系统为关键代谢途径提供还原力。疟原虫 falciparum Fd（PfFd）和 FNR（PfFNR）之间的电子转移比植物 Fd 和 FNR 的亲和力和特异性更高。我们通过关注 PfFd 的 Plasumodium 特异性区域来研究这种优越的蛋白质-蛋白质相互作用的结构基础。通过在植物 Fd 和 PfFd 之间交换 C 末端的三个残基，揭示了 PfFd 的 C 末端区域对与 PfFNR 进行电子转移的重要贡献。对 PfFd C 末端残基的进一步定点突变表明，在位置 96 和 97 处存在芳香族残基有助于降低 PfFNR 的 Km。使用荧光和量热测量的物理结合分析支持了这些结果。最近有报道称，PfFd 位置 97 的天冬氨酸突变为酪氨酸与疟原虫对青蒿素（抗疟一线药物）的耐药性密切相关。因此，PfFd D97Y 蛋白与 PfFNR 的增强相互作用可能与人类疟原虫对青蒿素的耐药性有关。
