title: Twin-arginine-dependent translocation of folded proteins.
abstract: Twin-arginine translocation (Tat) denotes a protein transport pathway in bacteria, archaea and plant chloroplasts, which is specific for precursor proteins harbouring a characteristic twin-arginine pair in their signal sequences. Many Tat substrates receive cofactors and fold prior to translocation. For a subset of them, proofreading chaperones coordinate maturation and membrane-targeting. Tat translocases comprise two kinds of membrane proteins, a hexahelical TatC-type protein and one or two members of the single-spanning TatA protein family, called TatA and TatB. TatC- and TatA-type proteins form homo- and hetero-oligomeric complexes. The subunits of TatABC translocases are predominantly recovered from two separate complexes, a TatBC complex that might contain some TatA, and a homomeric TatA complex. TatB and TatC coordinately recognize twin-arginine signal peptides and accommodate them in membrane-embedded binding pockets. Advanced binding of the signal sequence to the Tat translocase requires the proton-motive force (PMF) across the membranes and might involve a first recruitment of TatA. When targeted in this manner, folded twin-arginine precursors induce homo-oligomerization of TatB and TatA. Ultimately, this leads to the formation of a transmembrane protein conduit that possibly consists of a pore-like TatA structure. The translocation step again is dependent on the PMF.
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Stefan-Meier-Strasse 17, 79104 Freiburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Fröbel
authors.forename: Patrick
authors.initials: P
authors.lastname: Rose
authors.forename: Matthias
authors.initials: M
authors.lastname: Müller
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry; D003600:Cytosol / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D026901:Membrane Transport Proteins / Q000737:chemistry*; D011485:Protein Binding; D017510:Protein Folding; D021382:Protein Sorting Signals; D021381:Protein Transport; D018892:Proton-Motive Force; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C499697:TatA protein, E coli; C473116:TatB protein, E coli; C461379:TatC protein, E coli