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The zinc-responsive regulon of Neisseria meningitidis comprises 17 genes under control of a Zur element.

ABSTRACT: Zinc is a bivalent cation essential for bacterial growth and metabolism. The human pathogen Neisseria meningitidis expresses a homologue of the Zinc uptake regulator Zur, which has been postulated to repress the putative zinc uptake protein ZnuD. In this study, we elucidated the transcriptome of meningococci in response to zinc by microarrays and quantitative real-time PCR (qRT-PCR). We identified 15 genes that were repressed and two genes that were activated upon zinc addition. All transcription units (genes and operons) harbored a putative Zur binding motif in their promoter regions. A meningococcal Zur binding consensus motif (Zur box) was deduced in silico, which harbors a conserved central palindrome consisting of hexameric inverted repeats separated by three nucleotides (TGTTATDNHATAACA). In vitro binding of recombinant meningococcal Zur to this Zur box was shown for the first time using electrophoretic mobility shift assays. Zur binding to DNA depended specifically on the presence of zinc and was sensitive to mutations in the palindromic sequence. The Zur regulon among genes of unknown function comprised genes involved in zinc uptake, tRNA modification, and ribosomal assembly. In summary, this is the first study of the transcriptional response to zinc in meningococci.

SUBMITTER: Pawlik MC

PROVIDER: S-EPMC3497534 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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The zinc-responsive regulon of Neisseria meningitidis comprises 17 genes under control of a Zur element.

Pawlik Marie-Christin MC Hubert Kerstin K Joseph Biju B Claus Heike H Schoen Christoph C Vogel Ulrich U

Journal of bacteriology 20121005 23

Zinc is a bivalent cation essential for bacterial growth and metabolism. The human pathogen Neisseria meningitidis expresses a homologue of the Zinc uptake regulator Zur, which has been postulated to repress the putative zinc uptake protein ZnuD. In this study, we elucidated the transcriptome of meningococci in response to zinc by microarrays and quantitative real-time PCR (qRT-PCR). We identified 15 genes that were repressed and two genes that were activated upon zinc addition. All transcriptio ...[more]

PMID: 23043002

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Project description: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 Δzur 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 cobW1 gene, encoding a putative zinc chaperone, proved to be required for complete repression of cobW1 and its downstream genes in cells cultivated in mineral salts medium. A Zur box upstream of each of zur-cobW2, cobW3, 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.

Project description:BackgroundZinc is considered as an essential element for all living organisms, but it can be toxic at large concentrations. Bacteria therefore tightly regulate zinc metabolism. The Cg2502 protein of Corynebacterium glutamicum was a candidate to control zinc metabolism in this species, since it was classified as metalloregulator of the zinc uptake regulator (Zur) subgroup of the ferric uptake regulator (Fur) family of DNA-binding transcription regulators.ResultsThe cg2502 (zur) gene was deleted in the chromosome of C. glutamicum ATCC 13032 by an allelic exchange procedure to generate the zur-deficient mutant C. glutamicum JS2502. Whole-genome DNA microarray hybridizations and real-time RT-PCR assays comparing the gene expression in C. glutamicum JS2502 with that of the wild-type strain detected 18 genes with enhanced expression in the zur mutant. The expression data were combined with results from cross-genome comparisons of shared regulatory sites, revealing the presence of candidate Zur-binding sites in the mapped promoter regions of five transcription units encoding components of potential zinc ABC-type transporters (cg0041-cg0042/cg0043; cg2911-cg2912-cg2913), a putative secreted protein (cg0040), a putative oxidoreductase (cg0795), and a putative P-loop GTPase of the COG0523 protein family (cg0794). Enhanced transcript levels of the respective genes in C. glutamicum JS2502 were verified by real-time RT-PCR, and complementation of the mutant with a wild-type zur gene reversed the effect of differential gene expression. The zinc-dependent expression of the putative cg0042 and cg2911 operons was detected in vivo with a gfp reporter system. Moreover, the zinc-dependent binding of purified Zur protein to double-stranded 40-mer oligonucleotides containing candidate Zur-binding sites was demonstrated in vitro by DNA band shift assays.ConclusionWhole-genome expression profiling and DNA band shift assays demonstrated that Zur directly represses in a zinc-dependent manner the expression of nine genes organized in five transcription units. Accordingly, the Zur (Cg2502) protein is the key transcription regulator for genes involved in zinc homeostasis in C. glutamicum.

Dataset Information

The zinc-responsive regulon of Neisseria meningitidis comprises 17 genes under control of a Zur element.

Publications

The zinc-responsive regulon of Neisseria meningitidis comprises 17 genes under control of a Zur element.

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