title: The glove-like structure of the conserved membrane protein TatC provides insight into signal sequence recognition in twin-arginine translocation.
abstract: In bacteria, two signal-sequence-dependent secretion pathways translocate proteins across the cytoplasmic membrane. Although the mechanism of the ubiquitous general secretory pathway is becoming well understood, that of the twin-arginine translocation pathway, responsible for translocation of folded proteins across the bilayer, is more mysterious. TatC, the largest and most conserved of three integral membrane components, provides the initial binding site of the signal sequence prior to pore assembly. Here, we present two crystal structures of TatC from the thermophilic bacteria Aquifex aeolicus at 4.0 Å and 6.8 Å resolution. The membrane architecture of TatC includes a glove-shaped structure with a lipid-exposed pocket predicted by molecular dynamics to distort the membrane. Correlating the biochemical literature to these results suggests that the signal sequence binds in this pocket, leading to structural changes that facilitate higher order assemblies.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Sureshkumar
authors.initials: S
authors.lastname: Ramasamy
authors.forename: Ravinder
authors.initials: R
authors.lastname: Abrol
authors.forename: Christian J M
authors.initials: CJ
authors.lastname: Suloway
authors.forename: William M
authors.initials: WM
authors.lastname: Clemons
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics*; D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D017510:Protein Folding; D021382:Protein Sorting Signals
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D001120:Arginine