Differential interactions between a twin-arginine signal peptide and its translocase in Escherichia coli.
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.
Alami
Meriem
M
Institut für Biochemie und Molekularbiologie and Universität Freiburg, Hermann-Herder-Strasse 7, D-79104, Freiburg, Germany.
Lüke
Iris
I
Deitermann
Sandra
S
Eisner
Gottfried
G
Koch
Hans-Georg
HG
Brunner
Joseph
J
Müller
Matthias
M
D002462:Cell Membrane / Q000201:enzymology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D011498:Protein Precursors / Q000378:metabolism; D021382:Protein Sorting Signals / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011522:Protons; D015398:Signal Transduction / Q000502:physiology; D022161:Transport Vesicles / Q000378:metabolism
D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011522:Protons; C499697:TatA protein, E coli; C473116:TatB protein, E coli; C461379:TatC protein, E coli; C408585:twin-arginine translocase complex, E coli