title: Novel phenotypes of Escherichia coli tat mutants revealed by global gene expression and phenotypic analysis.
abstract: The Tat protein export system serves to export folded proteins harboring an N-terminal twin arginine signal peptide across the cytoplasmic membrane. In this study, we have used gene expression profiling of Escherichia coli supported by phenotypic analysis to investigate how cells respond to a defect in the Tat pathway. Previous work has demonstrated that strains mutated in genes encoding essential Tat pathway components are defective in the integrity of their cell envelope because of the mislocalization of two amidases involved in cell wall metabolism (Ize, B., Stanley, N. R., Buchanan, G., and Palmer, T. (2003) Mol. Microbiol. 48, 1183-1193). To distinguish between genes that are differentially expressed specifically because of the cell envelope defect and those that result from other effects of the tatC deletion, we also analyzed two different transposon mutants of the DeltatatC strain that have their outer membrane integrity restored. Approximately 50% of the genes that were differentially expressed in the tatC mutant are linked to the envelope defect, with the products of many of these genes involved in self-defense or protection mechanisms, including the production of exopolysaccharide. Among the changes that were not explicitly linked to envelope integrity, we characterized a role for the Tat system in iron acquisition and copper homeostasis. Finally, we have demonstrated that overproduction of the Tat substrate SufI saturates the Tat translocon and produces effects on global gene expression that are similar to those resulting from the DeltatatC mutation.
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
authors.forename: Bérengère
authors.initials: B
authors.lastname: Ize
authors.forename: Ida
authors.initials: I
authors.lastname: Porcelli
authors.forename: Sacha
authors.initials: S
authors.lastname: Lucchini
authors.forename: Jay C
authors.initials: JC
authors.lastname: Hinton
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms; D003300:Copper / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism; D033902:Periplasmic Binding Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D021381:Protein Transport / Q000502:physiology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003470:Culture Media; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D033902:Periplasmic Binding Proteins; C473632:SufI protein, E coli; C408585:twin-arginine translocase complex, E coli; C069969:fhuD protein, E coli; D003300:Copper; D007501:Iron; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase