Ketprasit Nutpakal, Tai Chia-Wei, Sharma Vivek Kumar, Manickam Yogavel, Khandokar Yogesh, Ye Xi, Dogovski Con, Hilko David H, Morton Craig J, Braun Anne-Sophie C, Leeming Michael G, Siddharam Bagale, Shami Gerald J, Pradeepkumar Pushpangadan Indira, Panjikar Santosh, Poulsen Sally-Ann, Griffin Michael D W, Sharma Amit, Tilley Leann, Xie Stanley C
Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Australia.
Molecular Medicine - Structural Parasitology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
PLoS Pathog. 2025 Jul 8;21(7):e1013057. doi: 10.1371/journal.ppat.1013057. eCollection 2025 Jul.
Malaria poses an enormous threat to human health. With ever-increasing resistance to currently deployed antimalarials, new targets and starting point compounds with novel mechanisms of action need to be identified. Here, we explore the antimalarial activity of the Streptomyces sp natural product, 5'-O-sulfamoyl-2-chloroadenosine (dealanylascamycin, DACM) and compare it with the synthetic adenosine monophosphate (AMP) mimic, 5-O-sulfamoyladenosine (AMS). These nucleoside sulfamates exhibit potent inhibition of P. falciparum growth with an efficacy comparable to that of the current front-line antimalarial, dihydroartemisinin. Exposure of P. falciparum to DACM leads to inhibition of protein translation, driven by eIF2α phosphorylation. We show that DACM targets multiple aminoacyl-tRNA synthetases (aaRSs), including the cytoplasmic aspartyl tRNA synthetase (AspRS). The mechanism involves hijacking of the reaction product, leading to the formation of a tightly bound inhibitory amino acid-sulfamate conjugate. We show that recombinant P. falciparum and P. vivax AspRS are susceptible to hijacking by DACM and AMS, generating Asp-DACM and Asp-AMS adducts that stabilize these proteins. By contrast, human AspRS appears less susceptible to hijacking. X-ray crystallography reveals that apo P. vivax AspRS exhibits a stabilized flipping loop over the active site that is poised to bind substrates. By contrast, human AspRS exhibits disorder in an extended region around the flexible flipping loop as well as in a loop in motif II. These structural differences may underpin the decreased susceptibility of human AspRS to reaction-hijacking by DACM and AMS. Our work reveals Plasmodium AspRS as a promising antimalarial target and highlights structural features that underpin differences in the susceptibility of aaRSs to reaction hijacking inhibition.
疟疾对人类健康构成巨大威胁。随着对当前使用的抗疟药物的耐药性不断增加，需要确定具有新作用机制的新靶点和起始化合物。在此，我们探索了链霉菌属天然产物5'-O-氨磺酰基-2-氯腺苷（去丙氨酰杀念菌素，DACM）的抗疟活性，并将其与合成的单磷酸腺苷（AMP）类似物5-O-氨磺酰腺苷（AMS）进行比较。这些核苷氨磺酸盐对恶性疟原虫的生长具有强效抑制作用，其效力与当前一线抗疟药物双氢青蒿素相当。恶性疟原虫暴露于DACM会导致蛋白质翻译受到抑制，这是由eIF2α磷酸化驱动的。我们表明，DACM靶向多种氨酰-tRNA合成酶（aaRSs），包括细胞质天冬氨酰tRNA合成酶（AspRS）。其机制涉及劫持反应产物，导致形成紧密结合的抑制性氨基酸-氨磺酸盐共轭物。我们表明，重组恶性疟原虫和间日疟原虫AspRS易受DACM和AMS的劫持，生成稳定这些蛋白质的Asp-DACM和Asp-AMS加合物。相比之下，人AspRS似乎较不易被劫持。X射线晶体学显示，无配体的间日疟原虫AspRS在活性位点上方呈现出一个稳定的翻转环，该环准备结合底物。相比之下，人AspRS在柔性翻转环周围的延伸区域以及基序II中的一个环中表现出无序状态。这些结构差异可能是导致人AspRS对DACM和AMS反应劫持抑制敏感性降低的原因。我们的工作揭示了疟原虫AspRS是一个有前景的抗疟靶点，并突出了支撑aaRSs对反应劫持抑制敏感性差异的结构特征。
