A genetic analysis of in vivo selenate reduction by Salmonella enterica serovar Typhimurium LT2 and Escherichia coli K12.
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.
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, Scotland, UK.
David
D
Guymer
Julien
J
Maillard
Frank
F
Sargent
D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D048168:Escherichia coli K12 / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics*; D064586:Selenic Acid; D018036:Selenium Compounds / Q000378:metabolism*; D017384:Sequence Deletion
D002352:Carrier Proteins; C434268:DmsD protein, E coli; D029968:Escherichia coli Proteins; D047908:Intracellular Signaling Peptides and Proteins; D026901:Membrane Transport Proteins; D018036:Selenium Compounds; C408585:twin-arginine translocase complex, E coli; D010088:Oxidoreductases; C078108:selenate reductase; D064586:Selenic Acid