ABSTRACT
MmpL3, a resistance-nodulation-division (RND) superfamily transporter, has been implicated in the formation of the outer membrane of
Mycobacterium tuberculosis
; specifically, MmpL3 is required for the export of mycolic acids in the form of trehalose monomycolates (TMM) to the periplasmic space or outer membrane of
M. tuberculosis
. Recently, seven series of inhibitors identified by whole-cell screening against
M. tuberculosis
, including the antituberculosis drug candidate SQ109, were shown to abolish MmpL3-mediated TMM export. However, this mode of action was brought into question by the broad-spectrum activities of some of these inhibitors against a variety of bacterial and fungal pathogens that do not synthesize mycolic acids. This observation, coupled with the ability of three of these classes of inhibitors to kill nonreplicating
M. tuberculosis
bacilli, led us to investigate alternative mechanisms of action. Our results indicate that the inhibitory effects of adamantyl ureas, indolecarboxamides, tetrahydropyrazolopyrimidines, and the 1,5-diarylpyrrole BM212 on the transport activity of MmpL3 in actively replicating
M. tuberculosis
bacilli are, like that of SQ109, most likely due to their ability to dissipate the transmembrane electrochemical proton gradient. In addition to providing novel insights into the modes of action of compounds reported to inhibit MmpL3, our results provide the first explanation for the large number of pharmacophores that apparently target this essential inner membrane transporter.
摘要
MmpL3是一种抗性-结节-分裂(RND)超家族转运体,与结核分枝杆菌外膜的形成有关。
结核分枝杆菌
MmpL3 是一种抗性-结节-分裂(RND)超家族转运体,被认为与结核分枝杆菌外膜的形成有关。
结核杆菌
.最近,通过全细胞筛选发现了七种针对结核杆菌的系列抑制剂。
结核杆菌的抑制剂
包括候选抗结核药物 SQ109 在内的七种系列抑制剂都被证明可以取消 MmpL3 介导的 TMM 输出。然而,其中一些抑制剂对多种不合成霉酚酸的细菌和真菌病原体具有广谱活性,这使人们对这种作用模式产生了疑问。这一观察结果,加上其中三类抑制剂能够杀死不复制的
结核杆菌
杆菌的能力,促使我们研究其替代作用机制。我们的研究结果表明,金刚烷基脲类、吲哚羧酰胺类、四氢吡唑嘧啶类和 1,5-二芳基吡咯 BM212 对活跃复制的结核杆菌中 MmpL3 的转运活性具有抑制作用。
结核杆菌
与 SQ109 一样,它们对结核杆菌 MmpL3 转运活性的影响很可能是由于它们能够消散跨膜电化学质子梯度。除了对已报道的抑制 MmpL3 的化合物的作用模式提供了新的见解外,我们的研究结果还首次解释了为什么有大量药剂显然以这种重要的内膜转运体为靶标。