Research Division, Sumitomo Dainippon Pharma Co., Ltd., Konohana-ku, Osaka, Japan.
Health & Crop Sciences Research Laboratory, Sumitomo Chemical Co., Ltd., Takarazuka City, Hyogo, Japan.
PLoS One. 2018 Nov 19;13(11):e0207673. doi: 10.1371/journal.pone.0207673. eCollection 2018.
Quinone outside inhibitors (QoIs), which inhibit the mitochondrial respiratory system by binding to the Qo site of Complex III in fungi, are widely used as pesticides with broad spectrum antifungal activity. However, excessive use of QoIs leads to pesticide resistance through mutation of amino acid residues in the Qo site. Recently, metyltetraprole, a novel QoI that is effective against wild-type and resistant mutant fungi, was developed. Interestingly, metyltetraprole has a very similar structure to other QoIs, azoxystrobin and pyraclostrobin, which do not act on resistant mutants. However, it is unknown how slight structural differences in these inhibitors alter their effectiveness towards fungi with amino acid mutations in the Qo site of Complex III. Therefore, we studied the features of interactions of inhibitors effective towards resistant mutants by quantitatively comparing the interaction profiles of three QoIs at the atomic level. First, we reproduced the binding affinity by the thermodynamic integration (TI) method, which treated explicitly environmental molecules and considered the pseudo-binding pathway. As such, a good correlation (R2 = 0.74) was observed between the binding free energy calculated using the TI method and experimentally observed pIC50 value in 12 inhibitor-target pairs, including wild-type and mutant Complex III in two fungal species, Zymoseptoria tritici and Pyrenophora teres. Trajectory analysis of this TI calculation revealed that the effectiveness against resistant mutant fungi strongly depended on the interaction of constituent parts of the inhibitor disposed near the active center of the target protein. Specifically, the key in the effectiveness against resistant mutant fungi is that the corresponding component part, tetrazolinone moiety of metyltetraprole, traded off Coulomb and van der Waals interactions in response to subtle changes in the binding pose.
醌外抑制剂 (QoIs) 通过与真菌复合物 III 的 Qo 位点结合来抑制线粒体呼吸系统，被广泛用作具有广谱抗真菌活性的农药。然而，过量使用 QoIs 会导致通过 Qo 位点氨基酸残基的突变而产生抗药性。最近，开发了一种新型 QoI 甲基四唑，它对野生型和耐药突变真菌都有效。有趣的是，甲基四唑与其他 QoI（肟菌酯和吡唑醚菌酯）非常相似，后者对耐药突变体不起作用。然而，尚不清楚这些抑制剂的微小结构差异如何改变它们对复合物 III 的 Qo 位点氨基酸突变的真菌的有效性。因此，我们通过在原子水平上定量比较三种 QoI 的相互作用特性来研究对耐药突变体有效的抑制剂的特征。首先，我们通过热力学积分 (TI) 方法重现了结合亲和力，该方法明确处理环境分子并考虑了伪结合途径。因此，在 12 个抑制剂-靶对中，包括两种真菌物种（小麦叶枯病菌和禾谷镰刀菌）中的野生型和突变型复合物 III，观察到使用 TI 方法计算的结合自由能与实验观察到的 pIC50 值之间存在良好的相关性（R2 = 0.74）。该 TI 计算的轨迹分析表明，对耐药突变体真菌的有效性强烈依赖于抑制剂的组成部分在靶蛋白活性中心附近的相互作用。具体而言，对抗耐药突变体真菌有效的关键是，相应的组成部分，甲基四唑的四唑啉酮部分，根据结合构象的细微变化，权衡库仑和范德华相互作用。
