title: TatD is a cytoplasmic protein with DNase activity. No requirement for TatD family proteins in sec-independent protein export.
abstract: The Escherichia coli Tat system mediates Sec-independent export of protein precursors bearing twin arginine signal peptides. Genes known to be involved in this process include tatA, tatB, and tatC that form an operon with a fourth gene, tatD. The tatD gene product has two homologues in E. coli coded by the unlinked ycfH and yjjV genes. An E. coli strain with in-frame chromosomal deletions in all three of tatD, ycfH, and yjjV exhibits no significant defect in the cellular location of five cofactor-containing enzymes that are synthesized with twin arginine signal peptides. Neither these mutations nor overproduction of the TatD protein cause any discernible effect on the export kinetics of an additional E. coli Tat pathway substrate. It is concluded that proteins of the TatD family have no obligate involvement in protein export by the Tat system. TatD is shown to be a cytoplasmic protein. TatD binds to immobilized Ni(2+) or Zn(2+) affinity columns and exhibits magnesium-dependent DNase activity. Features of the tatA operon that may control TatD expression are discussed.
authors.affiliation: Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Wexler
authors.forename: F
authors.initials: F
authors.lastname: Sargent
authors.forename: R L
authors.initials: RL
authors.lastname: Jack
authors.forename: N R
authors.initials: NR
authors.lastname: Stanley
authors.forename: E G
authors.initials: EG
authors.lastname: Bogsch
authors.forename: C
authors.initials: C
authors.lastname: Robinson
authors.forename: B C
authors.initials: BC
authors.lastname: Berks
authors.forename: T
authors.initials: T
authors.lastname: Palmer
mesh_terms: D001692:Biological Transport; D003593:Cytoplasm / Q000378:metabolism*; D004269:DNA, Bacterial; D003851:Deoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005092:Exonucleases / Q000378:metabolism*; D015696:Gene Products, tat / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D015696:Gene Products, tat; D011498:Protein Precursors; D003851:Deoxyribonucleases; D005092:Exonucleases; C000594605:TatD protein, E coli