A subset of bacterial inner membrane proteins integrated by the twin-arginine translocase

Mol Microbiol. 2003 Sep;49(5):1377-90. doi: 10.1046/j.1365-2958.2003.03642.x.

Abstract

A group of bacterial exported proteins are synthesized with N-terminal signal peptides containing a SRRxFLK 'twin-arginine' amino acid motif. Proteins bearing twin-arginine signal peptides are targeted post-translationally to the twin-arginine translocation (Tat) system which transports folded substrates across the inner membrane. In Escherichia coli, most integral inner membrane proteins are assembled by a co-translational process directed by SRP/FtsY, the SecYEG translocase, and YidC. In this work we define a novel class of integral membrane proteins assembled by a Tat-dependent mechanism. We show that at least five E. coli Tat substrate proteins contain hydrophobic C-terminal transmembrane helices (or 'C-tails'). Fusions between the identified transmembrane C-tails and the exclusively Tat-dependent reporter proteins TorA and SufI render the resultant chimeras membrane-bound. Export-linked signal peptide processing and membrane integration of the chimeras is shown to be both Tat-dependent and YidC-independent. It is proposed that the mechanism of membrane integration of proteins by the Tat system is fundamentally distinct from that employed for other bacterial inner membrane proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters*
  • Artificial Gene Fusion
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Membrane / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Genes, Reporter / genetics
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Oxidoreductases, N-Demethylating / genetics
  • Protein Sorting Signals*
  • Protein Transport
  • Recombinant Proteins / metabolism

Substances

  • ATP-Binding Cassette Transporters
  • Carrier Proteins
  • Escherichia coli Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Protein Sorting Signals
  • Recombinant Proteins
  • SufI protein, E coli
  • YIDC protein, E coli
  • nikA protein, E coli
  • twin-arginine translocase complex, E coli
  • Oxidoreductases, N-Demethylating
  • trimethylamine dehydrogenase