Competition between Sec- and TAT-dependent protein translocation in Escherichia coli

S. Cristóbal, J.-W. de Gier, Henrik Nielsen, G. von Heijne

    Research output: Contribution to journalJournal articleResearchpeer-review


    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.
    Original languageEnglish
    JournalThe EMBO Journal
    Issue number11
    Pages (from-to)2982-2990
    Publication statusPublished - 1999


    • Membrane protein
    • Protein secretion
    • Sec pathway
    • TAT pathway

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