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Monitoring the Assembly of a Secreted Bacterial Virulence Factor Using Site-specific Crosslinking
Published on: December 17, 2013
Differential interactions between a twin-arginine signal peptide and its translocase in Escherichia coli
Meriem Alami1, Iris Lüke, Sandra Deitermann
1Institut für Biochemie und Molekularbiologie and Universität Freiburg, Hermann-Herder-Strasse 7, D-79104, Freiburg, Germany.
Abstract:
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.
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