Copper transport in Mycobacterium tuberculosis

结核分枝杆菌在杀菌环境中生存能力的关键组成部分，如结核杆菌的吞噬小体 巨噬细胞是由其特殊的外膜(OM)建立的有效的通透性屏障。我们有 发现缺少OM通道蛋白Rv1698的Mtb突变体对铜更敏感。 铜是一种必不可少的微量营养素，但过量的铜是有毒的。细胞内铜浓度的变化 Rv1698突变体的突变倍数增加了100倍。我们的实验表明，铜需要Rv1698 通过OM外流，维持较低的细胞内铜水平。因为外流对一个 浓度梯度需要能量，大肠杆菌外排系统的OM组件连接到内部 为转运过程提供底物专一性和能量的膜泵。然而，它是 不知道结核分枝杆菌是如何排出废物分子、药物和其他有毒溶质的。Rv1698是第一个OM 任何分枝杆菌外排系统的组成部分，因此代表着一个极好的机会，不仅 研究Mtb如何控制必要的、但有毒的氧化还原活性金属，如铜，以及 一般情况下，是MTB。 干扰素刺激巨噬细胞时，含结核分枝杆菌吞噬小体内的铜增加 足以抑制结核分枝杆菌生长的浓度表明铜的稳态对 结核分枝杆菌的毒力。然而，对于Mtb来说，这在很大程度上是一个未开发的领域。因此，我们建议将 新的铜外排通道MctB和相互作用蛋白，以识别铜的缺失成分 并评估它们在结核分枝杆菌毒力中的作用。

A crucial component in the ability of Mtb to survive in bactericidal environments such as the phagosome of macrophages is the efficient permeability barrier established by its unusual outer membrane (OM). We have discovered that an Mtb mutant lacking the OM channel protein Rv1698 was more susceptible to copper. Copper is an essential micronutrient, but excess copper is toxic. The intracellular copper concentration of the rv1698 mutant was 100-fold increased. Our experiments demonstrated that Rv1698 is required for copper efflux across the OM and for maintaining low intracellular copper levels. Because efflux against a concentration gradient requires energy, the OM component of efflux systems in E. coli is connected to an inner membrane pump which contributes substrate specificity and energy to the transport process. However, it is unknown how Mtb extrudes waste molecules, drugs, and other toxic solutes. Rv1698 is the first OM component of any efflux system in mycobacteria and, hence, represents a great opportunity not only to examine how Mtb controls essential, but toxic redox-active metals such as copper, but also efflux processes in Mtb in general. Copper inside Mtb-containing phagosomes is increased upon stimulation of macrophages with interferon-¿ to concentrations that are sufficient to inhibit growth of Mtb indicating that copper homeostasis is critical for virulence of Mtb. However, this is a largely unexplored field for Mtb. We, therefore, propose to characterize the novel copper efflux channel MctB and interacting proteins, to identify missing components of copper homeostasis and to assess their role in virulence of Mtb.