Twin-arginine-dependent translocation of SufI in the absence of cytosolic helper proteins.
The twin-arginine translocation (Tat) machinery present in bacterial and thylakoidal membranes is able to transport fully folded proteins. Folding of some Tat precursor proteins requires dedicated chaperones that also sequester the signal sequence during the maturation process. Whether or not signal sequence-binding chaperones are a general prerequisite for all Tat substrate proteins is not known. Here, we have studied the propensity of Tat signal sequences of Escherichia coli to interact with general chaperones and peptidyl-prolyl-cis,trans-isomerases. Site-specific photocross-linking revealed a clear specificity for FK506-binding proteins. Nevertheless transport of the Tat substrate SufI into inverted inner membrane vesicles of E. coli was found to occur in the bona fide absence of any cytosolic chaperone. Our results suggest that in E. coli, cytosolic chaperones are not essential for the twin-arginine-dependent export of cofactor-less substrates.
Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany.
Eva
E
Holzapfel
Michael
M
Moser
Emile
E
Schiltz
Takuya
T
Ueda
Jean-Michel
JM
Betton
Matthias
M
Müller
D001120:Arginine; D003600:Cytosol / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport; D022021:Tacrolimus Binding Proteins / Q000378:metabolism
D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; C473632:SufI protein, E coli; C499697:TatA protein, E coli; C408585:twin-arginine translocase complex, E coli; D001120:Arginine; D022021:Tacrolimus Binding Proteins