SQ109 Targets MmpL3, a Membrane Transporter of Trehalose Monomycolate Involved in Mycolic Acid Donation to the Cell Wall Core of Mycobacterium tuberculosis
SQ109 Targets MmpL3, a Membrane Transporter of Trehalose Monomycolate Involved in Mycolic Acid Donation to the Cell Wall Core of Mycobacterium tuberculosis
复制标题
DOI：
10.1128/aac.05708-11
复制
发表时间：
2012-04-01
影响因子：
4.9
通讯作者：
Boshoff, Helena I.
中科院分区：
文献类型：
--
作者：
Tahlan, Kapil;Wilson, Regina;Boshoff, Helena I.
SQ 109是一种与乙胺丁醇有关的1，2-二胺，目前正在进行治疗结核病的临床试验，但其作用方式仍不清楚。在这里，我们证明SQ 109破坏细胞壁组装，大分子掺入试验和超微结构分析证明。SQ 109干扰分枝菌酸组装到结核分枝杆菌的细胞壁核心中，因为暴露于SQ 109的杆菌显示海藻糖二分枝菌酸酯（TDM）产生的立即抑制，并且不能将分枝菌酸酯附着到细胞壁阿拉伯半乳聚糖。这些影响不是由于抑制霉菌酸盐合成所致，因为总霉菌酸盐水平未受影响，而是导致海藻糖单霉菌酸盐（TMM）（TDM和细胞壁霉菌酸盐的前体）蓄积。在体外试验中使用纯化的酶表明，这不是由于抑制分泌的Ag 85分枝菌酰转移酶。我们无法实现SQ 109抗性突变体的自发产生;然而，导致TDM合成类似关闭并伴随TMM积累的该化合物的类似物用于自发产生也对SQ 109交叉抗性的抗性突变体。对这些突变体的全基因组测序表明，这些突变体都在编码跨膜转运蛋白的必需mmpL 3基因中存在突变。我们的研究结果表明，MmpL 3是SQ 109的目标，MmpL 3是分枝杆菌TMM的转运蛋白。
SQ109, a 1,2-diamine related to ethambutol, is currently in clinical trials for the treatment of tuberculosis, but its mode of action remains unclear. Here, we demonstrate that SQ109 disrupts cell wall assembly, as evidenced by macromolecular incorporation assays and ultrastructural analyses. SQ109 interferes with the assembly of mycolic acids into the cell wall core of Mycobacterium tuberculosis, as bacilli exposed to SQ109 show immediate inhibition of trehalose dimycolate (TDM) production and fail to attach mycolates to the cell wall arabinogalactan. These effects were not due to inhibition of mycolate synthesis, since total mycolate levels were unaffected, but instead resulted in the accumulation of trehalose monomycolate (TMM), the precursor of TDM and cell wall mycolates. In vitro assays using purified enzymes showed that this was not due to inhibition of the secreted Ag85 mycolyltransferases. We were unable to achieve spontaneous generation of SQ109-resistant mutants; however, analogs of this compound that resulted in similar shutdown of TDM synthesis with concomitant TMM accumulation were used to spontaneously generate resistant mutants that were also cross-resistant to SQ109. Whole-genome sequencing of these mutants showed that these all had mutations in the essential mmpL3 gene, which encodes a transmembrane transporter. Our results suggest that MmpL3 is the target of SQ109 and that MmpL3 is a transporter of mycobacterial TMM.