Separate analysis of twin-arginine translocation (Tat)-specific membrane binding and translocation in Escherichia coli |
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Authors: | Alami Meriem Trescher Dorothea Wu Long-Fei Müller Matthias |
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Affiliation: | Institut für Biochemie und Molekularbiologie, Universit?t Freiburg, Hermann-Herderstrasse 7, D-79104 Freiburg, Germany. |
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Abstract: | The twin-arginine translocation (Tat) pathway exports those precursor proteins to the periplasmic space of bacteria that harbor a twin-arginine (RR) consensus motif in their signal sequences. We have reproduced translocation of several Tat substrates into inside-out plasma membrane vesicles from Escherichia coli. Translocation proceeding at an efficiency of up to 20% occurs specifically via the Tat pathway as indicated by (i) its requirement for elevated levels of the TatABC proteins in the membrane vesicles, (ii) competition by an intact twin-arginine signal peptide, and (iii) susceptibility toward dissipation of the transmembrane H(+) gradient. The latter treatment, while blocking translocation, still allows for functional membrane association of Tat precursors. This is shown by the finding that translocation of isolated membrane-bound Tat precursor is restored upon re-energization of the vesicles. |
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