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A subset of bacterial inner membrane proteins integrated by the twin‐arginine translocase
Author(s) -
Hatzixanthis Kostas,
Palmer Tracy,
Sargent Frank
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03642.x
Subject(s) - translocase , twin arginine translocation pathway , biology , integral membrane protein , signal peptide , transmembrane protein , membrane protein , biochemistry , protein targeting , transmembrane domain , transport protein , inner membrane , signal recognition particle , peptide sequence , membrane transport protein , microbiology and biotechnology , membrane , chromosomal translocation , receptor , gene
Summary 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.