title: Genetic evidence for a tight cooperation of TatB and TatC during productive recognition of twin-arginine (Tat) signal peptides in Escherichia coli.
abstract: The twin arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane of bacteria. Tat signal peptides contain a consensus motif (S/T-R-R-X-F-L-K) that is thought to play a crucial role in substrate recognition by the Tat translocase. Replacement of the phenylalanine at the +2 consensus position in the signal peptide of a Tat-specific reporter protein (TorA-MalE) by aspartate blocked export of the corresponding TorA(D(+2))-MalE precursor, indicating that this mutation prevents a productive binding of the TorA(D(+2)) signal peptide to the Tat translocase. Mutations were identified in the extreme amino-terminal regions of TatB and TatC that synergistically suppressed the export defect of TorA(D(+2))-MalE when present in pairwise or triple combinations. The observed synergistic suppression activities were even more pronounced in the restoration of membrane translocation of another export-defective precursor, TorA(KQ)-MalE, in which the conserved twin arginine residues had been replaced by lysine-glutamine. Collectively, these findings indicate that the extreme amino-terminal regions of TatB and TatC cooperate tightly during recognition and productive binding of Tat-dependent precursor proteins and, furthermore, that TatB and TatC are both involved in the formation of a specific signal peptide binding site that reaches out as far as the end of the TatB transmembrane segment.
authors: Institut für Bio- und Geowissenschaften 1, Biotechnologie, Forschungszentrum Jülich GmbH, Jülich, Germany.
authors: Frank
authors: F
authors: Lausberg
authors: Stefan
authors: S
authors: Fleckenstein
authors: Peter
authors: P
authors: Kreutzenbeck
authors: Julia
authors: J
authors: Fröbel
authors: Patrick
authors: P
authors: Rose
authors: Matthias
authors: M
authors: Müller
authors: Roland
authors: R
authors: Freudl
mesh_terms: D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry; D021382:Protein Sorting Signals
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C473116:TatB protein, E coli; C461379:TatC protein, E coli; D010649:Phenylalanine