Tellurite reductase activity of nitrate reductase is responsible for the basal resistance of Escherichia coli to tellurite.
Tellurite and selenate reductase activities were identified in extracts of Escherichia coli. These activities were detected on non-denaturing polyacrylamide gels using an in situ methyl viologen activity-staining technique. The activity bands produced from membrane-protein extracts had the same RF values as those of nitrate reductases (NRs) A and Z. Tellurite and selenate reductase activities were absent from membranes obtained from mutants deleted in NRs A and Z. Further evidence of the tellurite and selenate reductase activities of NR was demonstrated using rocket immunoelectrophoresis analysis, where the tellurite and selenate reductase activities corresponded to the precipitation arc of NR. Additionally, hypersensitivity to potassium tellurite was observed under aerobic growth conditions in nar mutants. The tac promoter expression of NR A resulted in elevated tellurite resistance. The data obtained also imply that a minimal threshold level of NR A is required to increase resistance. Under anaerobic growth conditions additional tellurite reductase activity was identified in the soluble fraction on non-denaturing gels. Nitrate reductase mutants were not hypersensitive under anaerobic conditions, possibly due to the presence of this additional reductase activity.
Avazéri
Cécile
C
Laboratoire de Bioénergétique Cellulaire, Département d'Ecophysiologie Végétale et Microbiologie, CEA Cadarache, 13108 Saint Paul lez Durance, France.
Turner
Raymond J
RJ
MRC Group in the Molecular Biology of Membranes, Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7Canada.
Pommier
Jeanine
J
Laboratoire de Chimie Bactérienne, CNRS, 31 Chemin Joseph Augier, 13402 Marseille Cedex 20, France.
Weiner
Joël H
JH
MRC Group in the Molecular Biology of Membranes, Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7Canada.
Giordano
Gérard
G
Laboratoire de Chimie Bactérienne, CNRS, 31 Chemin Joseph Augier, 13402 Marseille Cedex 20, France.
Verméglio
André
A
Laboratoire de Bioénergétique Cellulaire, Département d'Ecophysiologie Végétale et Microbiologie, CEA Cadarache, 13108 Saint Paul lez Durance, France.
D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000502:physiology*; D008566:Membranes / Q000201:enzymology; D009154:Mutation; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D013691:Tellurium / Q000378:metabolism* / Q000494:pharmacology
D010088:Oxidoreductases; C056378:tellurite reductase; D009565:Nitrate Reductases; D050901:Nitrate Reductase; C078108:selenate reductase; C026660:tellurous acid; D013691:Tellurium