An alternative model of the twin arginine translocation system.
The twin arginine translocation (Tat) system is a machinery which can translocate folded proteins across energy transducing membranes. Currently it is supposed that Tat substrates bind directly to Tat translocon components before a ApH-driven translocation occurs. In this review, an alternative model is presented which proposes that membrane integration could precede Tat-dependent translocation. This idea is mainly supported by the recent observations of Tat-independent membrane insertion of Tat substrates in vivo and in vitro. Membrane insertion may allow i) a quality control of the folded state by membrane bound proteases like FtsH, ii) the recognition of the membrane spanning signal peptide by Tat system components, and iii) a pulling mechanism of translocation. In some cases of folded Tat substrates, the membrane targeting process may require ATP-dependent N-terminal unfolding-steps.
Brüser
Thomas
T
Institut für Mikrobiologie, Universitat Halle, D-06120 Halle, Germany. t.brueser@mikrobiologie.uni-halle.de
Sanders
Carsten
C
D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D011487:Protein Conformation; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000502:physiology; D013379:Substrate Specificity
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C408585:twin-arginine translocase complex, E coli