title: Signal peptide-chaperone interactions on the twin-arginine protein transport pathway.
abstract: The twin-arginine transport (Tat) system is a protein-targeting pathway of prokaryotes and chloroplasts. Most Escherichia coli Tat substrates are complex metalloenzymes that must be correctly folded and assembled before transport, and a preexport chaperone-mediated "proofreading" process is therefore in operation. The paradigm proofreading chaperone is TorD, which coordinates maturation and export of the key respiratory enzyme trimethylamine N-oxide reductase (TorA). It is demonstrated here that purified TorD binds tightly and with exquisite specificity to the TorA twin-arginine signal peptide in vitro. It is also reported that the TorD family constitutes a hitherto unexpected class of nucleotide-binding proteins. The affinity of TorD for GTP is enhanced by initial signal peptide binding, and it is proposed that GTP governs signal peptide binding-and-release cycles during Tat proofreading.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: Kostas
authors.initials: K
authors.lastname: Hatzixanthis
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clarke
authors.forename: Arthur
authors.initials: A
authors.lastname: Oubrie
authors.forename: David J
authors.initials: DJ
authors.lastname: Richardson
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
authors.forename: Frank
authors.initials: F
authors.lastname: Sargent
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D002151:Calorimetry; D003001:Cloning, Molecular; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000378:metabolism*; D005470:Fluorometry; D006160:Guanosine Triphosphate / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014461:Ultracentrifugation
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D021382:Protein Sorting Signals; C088083:TorD protein, E coli; C408585:twin-arginine translocase complex, E coli; D006160:Guanosine Triphosphate; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase; D008666:Metalloendopeptidases