The Novel Transcriptional Regulator SczA Mediates Protection Against Zn2+ Stress by Activation of the Zn2+-resistance Gene czcD in Streptococcus Pneumoniae

Mol Microbiol. 2007 Aug;65(4):1049-63. doi: 10.1111/j.1365-2958.2007.05849.x. Epub 2007 Jul 19.


Maintenance of the intracellular homeostasis of metal ions is important for the virulence of many bacterial pathogens. Here, we demonstrate that the czcD gene of the human pathogen Streptococcus pneumoniae is involved in resistance against Zn2+, and that its transcription is induced by the transition-metal ions Zn2+, Co2+ and Ni2+. Upstream of czcD a gene was identified, encoding a novel TetR family regulator, SczA, that is responsible for the metal ion-dependent activation of czcD expression. Transcriptome analyses revealed that in a sczA mutant expression of czcD, a gene encoding a MerR-family transcriptional regulator and a gene encoding a zinc-containing alcohol dehydrogenase (adhB) were downregulated. Activation of the czcD promoter by SczA is shown to proceed by Zn2+-dependent binding of SczA to a conserved DNA motif. In the absence of Zn2+, SczA binds to a second site in the czcD promoter, thereby fully blocking czcD expression. This is the first example of a metalloregulatory protein belonging to the TetR family that has been described. The presence in S. pneumoniae of the Zn2+-resistance system characterized in this study might reflect the need for adjustment to a fluctuating Zn2+ pool encountered by this pathogen during infection of the human body.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Bacterial Proteins / genetics*
  • Base Sequence
  • Cloning, Molecular
  • Conserved Sequence
  • DNA Footprinting
  • Gene Expression Regulation, Bacterial* / drug effects
  • Genes, Bacterial*
  • Genes, Regulator
  • Microarray Analysis
  • Models, Genetic
  • Molecular Sequence Data
  • Mutation / genetics
  • Operator Regions, Genetic
  • Operon / genetics
  • Promoter Regions, Genetic / genetics
  • Protein Binding / drug effects
  • Streptococcus pneumoniae / drug effects*
  • Streptococcus pneumoniae / genetics*
  • Streptococcus pneumoniae / growth & development
  • Transcription Factors / metabolism*
  • Transcription, Genetic / drug effects
  • Zinc / pharmacology*


  • Bacterial Proteins
  • Transcription Factors
  • Zinc