Abstract
The twin-arginine translocation (Tat) apparatus is a protein targeting system found in the cytoplasmic membranes of many prokaryotes. Substrate proteins of the Tat pathway are synthesised with signal peptides bearing SRRxFLK 'twin-arginine' amino acid motifs. All Tat signal peptides have a common tripartite structure comprising a polar N-terminal region, followed by a hydrophobic region of variable length and a polar C-terminal region. In Escherichia coli, Tat signal peptides are proteolytically cleaved after translocation. The signal peptide C-terminal regions contain conserved AxA motifs, which are possible recognition sequences for leader peptidase I (LepB). In this work, the role of LepB in Tat signal peptide processing was addressed directly. Deliberate repression of lepB expression prevented processing of all Tat substrates tested, including SufI, AmiC, and a TorA-23K reporter protein. In addition, electron microscopy revealed gross defects in cell architecture and membrane integrity following depletion of cellular LepB protein levels.
Original language | English |
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Pages (from-to) | 919-925 |
Number of pages | 7 |
Journal | Archives of Microbiology |
Volume | 191 |
Issue number | 12 |
DOIs | |
Publication status | Published - Dec 2009 |
Keywords
- Escherichia coli
- Tat protein transport pathway
- Signal peptidase I
- LepB protein
- OUTER-MEMBRANE
- EXPORT PATHWAY
- PROTEIN TRANSLOCATION
- CELL-ENVELOPE
- EXPRESSION
- INTEGRITY
- PROMOTER
- VECTORS
- SYSTEM
- OPERON