DnaK plays a pivotal role in Tat targeting of CueO and functions beside SlyD as a general Tat signal binding chaperone

authored by

Wenke Graubner, Angelika Schierhorn, Thomas Brüser

Abstract

The Tat (twin-arginine translocation) system from Escherichia coli transports folded proteins with N-terminal twin-arginine signal peptides across the cytoplasmic membrane. The influence of general chaperones on Tat substrate targeting has not been clarified so far. Here we show that the chaperones SlyD and DnaK bind to a broad range of different Tat signal sequences in vitro and in vivo. Initially, SlyD and GroEL were purified from DnaK-deficient extracts by their affinity to various Tat signal sequences. Of these, only SlyD bound Tat signal sequences also in the presence of DnaK. SlyD and DnaK also co-purified with Tat substrate precursors, demonstrating the binding to Tat signal sequences in vivo. Deletion of dnaK completely abolished Tat-dependent translocation of CueO, but not of DmsA, YcdB, or HiPIP, indicating that DnaK has an essential role specifically for CueO. DnaK was not required for stability of the CueO precursor and thus served in some essential step after folding. A CueO signal sequence fusion to HiPIP was Tat-dependently transported without the need of DnaK, indicating that the mature domain of CueO is responsible for the DnaK dependence. The overall results suggest that SlyD and DnaK are in the set of chaperones that can serve as general Tat signal-binding proteins. DnaK has additional functions that are indispensable for the targeting of CueO.

Organisation(s)

Institute of Microbiology

External Organisation(s)

Martin Luther University Halle-Wittenberg
Max Planck Research Unit for Enzymology of Protein Folding

Type

Article

Journal

Journal of Biological Chemistry

Volume

282

Pages

7116-7124

No. of pages

9

ISSN

0021-9258

Publication date

02.03.2007

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Biochemistry, Molecular Biology, Cell Biology

Electronic version(s)

https://doi.org/10.1074/jbc.M608235200 (Access: Open)