title: Moving folded proteins across the bacterial cell membrane.
abstract: The Tat protein export system is located in the bacterial cytoplasmic membrane and operates in parallel to the well-known Sec pathway. While the Sec system only transports unstructured substrates, the function of the Tat pathway is to translocate folded proteins. The Tat translocase thus faces the formidable challenge of moving structured macromolecular substrates across the bacterial cytoplasmic membrane without rendering the membrane freely permeable to protons and other ions. The substrates of the Tat pathway are often proteins that bind cofactor molecules in the cytoplasm, and are thus folded, prior to export. Such periplasmic cofactor-containing proteins are essential for most types of bacterial respiratory and photosynthetic energy metabolism. In addition, the Tat pathway is involved in outer membrane biosynthesis and in bacterial pathogenesis. Substrates are targeted to the Tat pathway by amino-terminal signal sequences harbouring consecutive, essentially invariant, arginine residues, and movement of proteins through the Tat system is energized by the transmembrane proton electrochemical gradient. The TatA protein probably forms the transport channel while the TatBC proteins act as a receptor complex that recognizes the signal peptide of the substrate protein.
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.|Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000235:genetics; D021381:Protein Transport
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C408585:twin-arginine translocase complex, E coli