Affiliation:
1. Molecular Microbiology, Institute for Biology/Microbiology, Martin Luther University Halle-Wittenberg, Halle, Germany
Abstract
ABSTRACT
Zinc is an essential trace element, yet it is toxic at high concentrations. In the betaproteobacterium
Cupriavidus metallidurans
, the highly efficient removal of surplus zinc from the periplasm is responsible for the outstanding metal resistance of the organism. Rather than having a typical Zur-dependent, high-affinity ATP-binding cassette transporter of the ABC protein superfamily for zinc uptake at low concentrations,
C. metallidurans
has the secondary zinc importer ZupT of the zinc-regulated transporter, iron-regulated transporter (ZRT/IRT)-like protein (ZIP) family. It is important to understand, therefore, how this zinc-resistant bacterium copes with exposure to low zinc concentrations. Members of the Zur regulon in
C. metallidurans
were identified by comparing the transcriptomes of a Δ
zur
mutant and its parent strain. The consensus sequence of the Zur-binding box was derived for the
zupTp
promoter-regulatory region by use of a truncation assay. The motif was used to predict possible Zur boxes upstream of Zur regulon members. The binding of Zur to these boxes was confirmed. Two Zur boxes upstream of the
cobW
1
gene, encoding a putative zinc chaperone, proved to be required for complete repression of
cobW
1
and its downstream genes in cells cultivated in mineral salts medium. A Zur box upstream of each of
zur-cobW
2
,
cobW
3
, and
zupT
permitted both low expression levels of these genes and their upregulation under conditions of zinc starvation. This demonstrates a compartmentalization of zinc homeostasis in
C. metallidurans
, where the periplasm is responsible for the removal of surplus zinc, cytoplasmic components are responsible for the management of zinc as an essential cofactor, and the two compartments are connected by ZupT.
IMPORTANCE
Elucidating zinc homeostasis is necessary for understanding both host-pathogen interactions and the performance of free-living bacteria in their natural environments.
Escherichia coli
acquires zinc under conditions of low zinc concentrations via the Zur-controlled ZnuABC importer of the ABC superfamily, and this was also the paradigm for other bacteria. In contrast, the heavy-metal-resistant bacterium
C. metallidurans
achieves high tolerance to zinc through sophisticated zinc handling and efflux systems operating on periplasmic zinc ions, so that removal of surplus zinc is a periplasmic feature in this bacterium. It is shown here that this process is augmented by the management of zinc by cytoplasmic zinc chaperones, whose synthesis is controlled by the Zur regulator. This demonstrates a new mechanism, involving compartmentalization, for organizing zinc homeostasis.
Funder
Deutsche Forschungsgemeinschaft
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
17 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献