Involvement of a putative molybdenum enzyme in the reduction of selenate by Escherichia coli

Microbiology (Reading). 2002 Dec;148(Pt 12):3865-3872. doi: 10.1099/00221287-148-12-3865.

Abstract

Selenium oxyanions, particularly selenite, can be highly toxic to living organisms. Few bacteria reduce both selenate and selenite into the less toxic elemental selenium. Insights into the mechanisms of the transport and the reduction of selenium oxyanions in Escherichia coli were provided by a genetic analysis based on transposon mutagenesis. Ten mutants impaired in selenate reduction were analysed. Three of them were altered in genes encoding transport proteins including a porin, an inner-membrane protein and a sulfate carrier. Two mutants were altered in genes required for molybdopterin biosynthesis, strongly suggesting that the selenate reductase of E. coli is a molybdoenzyme. However, mutants deleted in various oxomolybdenum enzymes described so far in this species still reduced selenate. Finally, a mutant in the gene ygfK encoding a putative oxidoreductase was obtained. This gene is located upstream of ygfN and ygfM in the ygfKLMN putative operon. YgfN and YgfM code for a molybdopterin-containing enzyme and a polypeptide carrying a FAD domain, respectively. It is therefore proposed that the selenate reductase of E. coli is a structural complex including the proteins YgfK, YgfM and YgfN. In addition, all the various mutants were still able to reduce selenite into elemental selenium. This implies that the transport and reduction of this compound are clearly distinct from those of selenate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Coenzymes*
  • DNA Transposable Elements
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Metalloproteins / genetics
  • Metalloproteins / metabolism*
  • Molybdenum Cofactors
  • Mutagenesis, Insertional
  • Operon
  • Oxidation-Reduction
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism*
  • Pteridines / metabolism*
  • Selenic Acid
  • Selenium Compounds / metabolism*
  • Sodium Selenite / metabolism

Substances

  • Coenzymes
  • DNA Transposable Elements
  • Escherichia coli Proteins
  • Metalloproteins
  • Molybdenum Cofactors
  • Pteridines
  • Selenium Compounds
  • molybdenum cofactor
  • Oxidoreductases
  • selenate reductase
  • Sodium Selenite
  • Selenic Acid