Diamide stress induces a metallothionein BmtA through a repressor BxmR and is modulated by Zn-inducible BmtA in the cyanobacterium Oscillatoria brevis

Kazunobu Hirose, Bunichi Ezaki, Tong Liu, Susumu Nakashima

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

A cysteine-rich metal binding protein MT (metallothionein) (named BmtA) is induced upon exposure to multiple heavy metal ions in the freshwater cyanobacterium Oscillatoria brevis. The SmtB/ArsR family repressor BxmR from O. brevis represses the expression of an operon encoding bmtA and bxmR. In the present study, the expression of bmtA was induced in vivo by diamide, a specific thiol oxidant, in O. brevis cells. In vitro electrophoretic gel mobility shift experiments revealed that the incubation with diamide induces disassembly of the BxmR-bxmR/bmtA operator (O)/promoter (P) complex [multiple resolvable complexes of BxmR with oligonucleotide (named P5) containing a single 12-2-12 inverted repeat derived from the O/P region of bxmR/bmtA]. Thus, the exposure to diamide induces MT mRNA in O. brevis, and this induction is associated with diamide-mediated inhibition of BxmR-P5 complex. BxmR is more sensitive to diamide than to H2O2. Furthermore, pretreatment of O. brevis with Zn decreased intracellular peroxidation products caused by diamide. Thus, these results imply that MT induced by Zn-pretreatment functions to protect O. brevis cells against diamide stress.

Original languageEnglish
Pages (from-to)250-256
Number of pages7
JournalToxicology Letters
Volume163
Issue number3
DOIs
Publication statusPublished - Jun 1 2006

Keywords

  • Cyanobacteria
  • Diamide
  • Metallothionein (MT)
  • Oscillatoria brevis
  • Oxidative stress
  • Repressor

ASJC Scopus subject areas

  • Toxicology

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