Copper transport in Mycobacterium tuberculosis

结核分枝杆菌在杀菌环境中生存能力的一个关键组成部分，如噬菌体。 巨噬细胞是由其不寻常的外膜（OM）建立的有效渗透屏障。我们有 发现缺乏OM通道蛋白Rv1698的Mtb突变体对铜更敏感。 铜是一种必需的微量营养素，但过量的铜是有毒的。细胞内铜离子浓度 RV1698突变体的细胞增殖增加了100倍。我们的实验表明，Rv1698是铜所必需的 外排穿过OM和维持低细胞内铜水平。因为对一个 浓度梯度需要能量，E.大肠杆菌连接到一个 膜泵，其为运输过程提供底物特异性和能量。但据 目前尚不清楚结核杆菌如何排出废物分子、药物和其他有毒溶质。Rv1698是第一个OM 分支杆菌中任何外排系统的组成部分，因此，不仅代表了一个很好的机会， 研究结核分枝杆菌如何控制必要的，但有毒的氧化还原活性金属，如铜，但也流出过程中， MTB一般 含结核分枝杆菌的吞噬体内的铜在用干扰素刺激巨噬细胞后增加， 浓度足以抑制结核分枝杆菌的生长，表明铜稳态对于结核分枝杆菌的生长至关重要。 结核分枝杆菌毒力然而，这是结核病的一个基本上未开发的领域。因此，我们建议将 新的铜流出通道MctB和相互作用的蛋白质，以确定铜的缺失成分 稳态，并评估其在Mtb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.