Molecular Microbiology, Institute for Biology/Microbiology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany.
Protein Biochemistry, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany.
J Bacteriol. 2019 Jul 10;201(15). doi: 10.1128/JB.00192-19. Print 2019 Aug 1.
The Zur regulon is central to zinc homeostasis in the zinc-resistant bacterium It comprises the transcription regulator Zur, the zinc importer ZupT, and three members of the COG0523 family of metal-chaperoning G3E-type GTPases, annotated as CobW1, CobW2, and CobW3. The operon structures of the and loci were determined. To analyze the interplay between the Zur regulon components and metal resistance, deletion mutants were constructed from the wild-type strain CH34 and various other strains. The Zur regulon components interacted with the plasmid-encoded and chromosomally encoded metal resistance factors to acquire metals from complexes of EDTA and for homeostasis of and resistance to zinc, nickel, cobalt, and cadmium. The three G3E-type GTPases were characterized in more detail. CobW1 bound only 1 Zn atom per mol of protein with a stability constant slightly above that of 2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene (Zincon) and an additional 0.5 Zn with low affinity. The CobW1 system was necessary to obtain metals from EDTA complexes. The GTPase CobW2 is a zinc storage compound and bound 0.5 to 1.5 Zn atoms tightly and up to 6 more with lower affinity. The presence of MgGTP unfolded the protein partially. CobW3 had no GTPase activity and equilibrated metal import by ZupT with that of the other metal transport systems. It sequestered 8 Zn atoms per mol with decreasing affinity. The three CobWs bound to the metal-dependent protein FolE, which is encoded directly downstream of This demonstrated an important contribution of the Zur regulon components to metal homeostasis in Zinc is an important transition metal cation and is present as an essential component in many enzymes, such as RNA polymerase. As with other transition metals, zinc is also toxic at higher concentrations so that living cells have to maintain strict control of their zinc homeostasis. Members of the COG0523 family of metal-chaperoning GE3-type GTPases exist in archaea, bacteria, and eucaryotes, including humans, and they may be involved in delivery of zinc to thousands of different proteins. We used a combination of molecular, physiological, and biochemical methods to demonstrate the important but diverse functions of COG0523 proteins in , which are produced as part of the Zur-controlled zinc starvation response in this bacterium.
Zur 调控子是锌抵抗菌中锌稳态的核心，它包括转录调节剂 Zur、锌转运蛋白 ZupT 和 COG0523 家族的三种金属伴侣 G3E 型 GTPase，分别注释为 CobW1、CobW2 和 CobW3。确定了 和 基因座的操纵子结构。为了分析 Zur 调控子成分与金属抗性之间的相互作用，从野生型菌株 CH34 和其他各种菌株中构建了缺失突变体。Zur 调控子成分与质粒编码和染色体编码的金属抗性因子相互作用，从 EDTA 配合物中获取金属，并维持锌、镍、钴和镉的稳态和抗性。更详细地描述了三种 G3E 型 GTPase。CobW1 与每个分子的蛋白质结合仅 1 个锌原子，稳定常数略高于 2-羧基-2'-羟基-5'-磺基苯并恶唑（Zincon），并以低亲和力结合另外 0.5 个锌。CobW1 系统是从 EDTA 配合物中获取金属所必需的。GTPase CobW2 是一种锌储存化合物，紧密结合 0.5 至 1.5 个锌原子，并以较低亲和力结合多达 6 个。MgGTP 的存在使蛋白质部分展开。CobW3 没有 GTPase 活性，通过 ZupT 与其他金属转运系统平衡金属输入。它与每个分子的蛋白质 FolE 结合，该蛋白质直接位于 下游，该蛋白编码 每个分子结合 8 个锌原子，亲和力逐渐降低。这表明 Zur 调控子成分对 的金属稳态有重要贡献。锌是一种重要的过渡金属阳离子，是许多酶（如 RNA 聚合酶）的必需组成部分。与其他过渡金属一样，锌在较高浓度下也具有毒性，因此活细胞必须严格控制其锌稳态。COG0523 家族的金属伴侣 G3E 型 GTPase 存在于古菌、细菌和真核生物中，包括人类，它们可能参与将锌递送至数千种不同的蛋白质。我们使用分子、生理和生化方法的组合，证明了 COG0523 蛋白在 中的重要但多样化的功能，这些蛋白是作为该细菌 Zur 控制的锌饥饿反应的一部分产生的。
