Differential Interactions between a Twin-Arginine Signal Peptide and Its Translocase in Escherichia coli

• Published in: Molecular cell Vol. 12; no. 4; pp. 937 - 946
• Main Authors: Alami, Meriem, Lüke, Iris, Deitermann, Sandra, Eisner, Gottfried, Koch, Hans-Georg, Brunner, Joseph, Müller, Matthias
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2003
• Subjects: Cell Membrane - enzymology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - metabolism; Escherichia coli Proteins - physiology; Membrane Transport Proteins - metabolism; Membrane Transport Proteins - physiology; Protein Precursors - metabolism; Protein Sorting Signals - physiology; Protein Structure, Tertiary - physiology; Protein Transport - physiology; Protons; Signal Transduction - physiology; TatA protein; TatB protein; TatC protein; translocase; Transport Vesicles - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/S1097-2765(03)00398-8

The twin-arginine translocation (Tat) machinery of the Escherichia coli inner membrane is dedicated to the export of proteins harboring a conserved SRRxFLK motif in their signal sequence. TatA, TatB, and TatC are the functionally essential constituents of the Tat machinery, but their precise function is unknown. Using site-specific crosslinking, we have analyzed interactions of the twin-arginine precursor preSufI with the Tat proteins upon targeting to inner membrane vesicles. TatA association is observed only in the presence of a transmembrane H+ gradient. TatB is found in contact with the entire signal sequence and adjacent parts of mature SufI. Interaction of TatC with preSufI is, however, restricted to a discrete area around the consensus motif. The results reveal a hierarchy in targeting of a Tat substrate such that for the primary interaction, TatC is both necessary and sufficient while a subsequent association with TatB likely mediates transfer from TatC to the actual Tat pore.