title: Competition between Sec- and TAT-dependent protein translocation in Escherichia coli.
abstract: Recently, a new protein translocation pathway, the twin-arginine translocation (TAT) pathway, has been identified in both bacteria and chloroplasts. To study the possible competition between the TAT- and the well-characterized Sec translocon-dependent pathways in Escherichia coli, we have fused the TorA TAT-targeting signal peptide to the Sec-dependent inner membrane protein leader peptidase (Lep). We find that the soluble, periplasmic P2 domain from Lep is re-routed by the TorA signal peptide into the TAT pathway. In contrast, the full-length TorA-Lep fusion protein is not re-routed into the TAT pathway, suggesting that Sec-targeting signals in Lep can override TAT-targeting information in the TorA signal peptide. We also show that the TorA signal peptide can be converted into a Sec-targeting signal peptide by increasing the hydrophobicity of its h-region. Thus, beyond the twin-arginine motif, the overall hydrophobicity of the signal peptide plays an important role in TAT versus Sec targeting. This is consistent with statistical data showing that TAT-targeting signal peptides in general have less hydrophobic h-regions than Sec-targeting signal peptides.
authors.affiliation: Department of Biochemistry, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Cristóbal
authors.forename: J W
authors.initials: JW
authors.lastname: de Gier
authors.forename: H
authors.initials: H
authors.lastname: Nielsen
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D019286:Endopeptidase K; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005998:Glycine / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D019897:Periplasm / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D013104:Spheroplasts / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D001120:Arginine; D019286:Endopeptidase K; D007930:Leucine; D005998:Glycine