A genetic analysis of in vivo selenate reduction by <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Typhimurium LT2 and <Emphasis Type="Italic">Escherichia coli</Emphasis> K12 |
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Authors: | David Guymer Julien Maillard Frank Sargent |
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Institution: | (1) Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, UK;(2) ENAC-ISTE/Laboratoire de Biotechnologie Environnementale (LBE), EPF Lausanne, Batiment Chimie-B Ecublens, CH-1015 Lausanne, Switzerland |
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Abstract: | The twin-arginine transport (Tat) system is dedicated to the translocation of folded proteins across the bacterial cytoplasmic
membrane. Proteins are targeted to the Tat system by signal peptides containing a twin-arginine motif. In Salmonella enterica serovar Typhimurium and Escherichia coli many Tat substrates are known or predicted to bind a molybdenum cofactor in the cytoplasm prior to export. In the case of
N- and S-oxide reductases, co-ordination of molybdenum cofactor insertion with protein export involves a ‘Tat proofreading’ process
where chaperones of the TorD family bind the signal peptides, thus preventing premature export. Here, a genetic approach was
taken to determine factors required for selenate reductase activity in Salmonella and E. coli. It is reported for both biological systems that an active Tat translocase and a TorD-like chaperone (DmsD) are required
for complete in vivo reduction of selenate to elemental red selenium. Further mutagenesis and in vitro biophysical experiments
implicate the Salmonella
ynfE gene product, and the E. coli YnfE and YnfF proteins, as putative Tat-targeted selenate reductases. |
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Keywords: | Enteric bacteria Bacterial respiration Twin-arginine translocation pathway Molybdo-enzymes Selenate reductase Molecular chaperone Mutagenesis Isothermal titration calorimetry |
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