Graded expression of zinc-responsive genes through two regulatory zinc-binding sites in Zur

Jung Ho Shin, Hoi Jong Jung, Young Jun An, Yoo Bok Cho, Sun Shin Cha, Jung Hye Roe

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

Zinc is one of the essential transition metals in cells. Excess or lack of zinc is detrimental, and cells exploit highly sensitive zinc-binding regulators to achieve homeostasis. In this article,we present a crystal structure of active Zur from Streptomyces coelicolor with three zinc-binding sites (C-, M-, and D-sites). Mutations of the three sites differentially affected sporulation and transcription of target genes, such that C- and M-site mutations inhibited sporulation and derepressed all target genes examined, whereas D-site mutations did not affect sporulation and derepressed only a sensitive gene. Biochemical and spectroscopic analyses of representativemetal sitemutants revealed that the C-site serves a structural role, whereas the M- and D-sites regulate DNA-binding activity as an on-off switch and a fine-tuner, respectively. Consistent with differential effect of mutations on target genes, zinc chelation by TPEN derepressed some genes (znuA, rpmF2) more sensitively than others (rpmG2, SCO7682) in vivo. Similar pattern of TPEN-sensitivity was observed for Zur-DNA complexes formed on different promoters in vitro. The sensitive promoters bound Zur with lower affinity than the less sensitive ones. EDTA-treated apo-Zur gained its DNA binding activity at different concentrations of added zinc for the two promoter groups, corresponding to free zinc concentrations of 4.5 × 10-16 M and 7.9 × 10-16 M for the less sensitive and sensitive promoters, respectively. The graded expression of target genes is a clever outcome of subtly modulating Zur-DNA binding affinities in response to zinc availability. It enables bacteria to detect metal depletion with improved sensitivity and optimize gene-expression pattern.

Original languageEnglish
Pages (from-to)5045-5050
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number12
DOIs
StatePublished - 22 Mar 2011

Keywords

  • Ferric uptake regulator
  • Graded transcription regulation
  • Regulatory metal

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