Molecular Microbiology, Institute for Biology/Microbiology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany.
Department of Environmental Analytical Chemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
J Bacteriol. 2024 Aug 22;206(8):e0022624. doi: 10.1128/jb.00226-24. Epub 2024 Jul 23.
The metal-resistant beta-proteobacterium is also able to survive conditions of metal starvation. We show that zinc-starved cells can substitute some of the required zinc with cobalt but not with nickel ions. The zinc importer ZupT was necessary for this process but was not essential for either zinc or cobalt import. The cellular cobalt content was also influenced by the two COG0523-family proteins, CobW2 and CobW3. Pulse-chase experiments with radioactive and isotope-enriched zinc demonstrated that both proteins interacted with ZupT to control the cellular flow-equilibrium of zinc, a central process of zinc homeostasis. Moreover, an antagonistic interplay of CobW2 and CobW3 in the presence of added cobalt caused a growth defect in mutant cells devoid of the cobalt efflux system DmeF. Full cobalt resistance also required a synergistic interaction of ZupT and DmeF. Thus, the two transporters along with CobW2 and CobW3 interact to control cobalt homeostasis in a process that depends on zinc availability. Because ZupT, CobW2, and CobW3 also direct zinc homeostasis, this process links the control of cobalt and zinc homeostasis, which subsequently protects against cadmium stress and general metal starvation.IMPORTANCEIn bacterial cells, zinc ions need to be allocated to zinc-dependent proteins without disturbance of this process by other transition metal cations. Under zinc-starvation conditions, floods the cell with cobalt ions, which protect the cell against cadmium toxicity, help withstand metal starvation, and provide cobalt to metal-promiscuous paralogs of essential zinc-dependent proteins. The number of cobalt ions needs to be carefully controlled to avoid a toxic cobalt overload. This is accomplished by an interplay of the zinc importer ZupT with the COG0523-family proteins, CobW3, and CobW2. At high external cobalt concentrations, this trio of proteins additionally interacts with the cobalt efflux system, DmeF, so that these four proteins form an inextricable link between zinc and cobalt homeostasis.
耐金属β变形菌也能够在金属饥饿的条件下存活。我们表明，缺锌细胞可以用钴替代一些必需的锌，但不能用镍离子替代。锌转运蛋白 ZupT 是这个过程所必需的，但对锌或钴的输入都不是必需的。细胞内钴含量也受两种 COG0523 家族蛋白 CobW2 和 CobW3 的影响。用放射性和同位素标记的锌进行脉冲追踪实验表明，这两种蛋白质都与 ZupT 相互作用，以控制锌的细胞流动平衡，这是锌稳态的一个核心过程。此外，在添加钴的情况下，CobW2 和 CobW3 之间的拮抗相互作用导致缺乏钴外排系统 DmeF 的突变细胞出现生长缺陷。完全的钴抗性还需要 ZupT 和 DmeF 的协同相互作用。因此，这两种转运蛋白与 CobW2 和 CobW3 相互作用，以控制一个依赖锌可用性的钴稳态过程。由于 ZupT、CobW2 和 CobW3 也指导锌稳态，这个过程将钴和锌稳态的控制联系起来，从而保护细胞免受镉胁迫和一般金属饥饿的影响。
在细菌细胞中，锌离子需要分配给依赖锌的蛋白质，而不会被其他过渡金属阳离子干扰这个过程。在缺锌条件下，细胞会被钴离子淹没，这些钴离子可以保护细胞免受镉毒性的影响，帮助细胞耐受金属饥饿，并为依赖锌的金属混杂的必需锌蛋白的平行物提供钴。需要小心控制钴离子的数量，以避免有毒的钴过载。这是通过锌转运蛋白 ZupT 与 COG0523 家族蛋白 CobW3 和 CobW2 的相互作用来实现的。在高外部钴浓度下，这三种蛋白还与钴外排系统 DmeF 相互作用，因此这四种蛋白在锌和钴稳态之间形成了一个不可分割的联系。
