Functional reconstitution of bacterial Tat translocation in vitro

The Tat (twin‐arginine translocation) pathway is a Sec‐independent mechanism for translocating folded preproteins across or into the inner membrane of Escherichia coli. To study Tat translocation, we sought an in vitro translocation assay using purified inner membrane vesicles and in vitro synthesiz...

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Bibliographic Details
Published in:The EMBO journal 2001-05, Vol.20 (10), p.2472-2479
Main Authors: Yahr, Timothy L., Wickner, William T.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Biological Transport
Carrier Proteins - genetics
Carrier Proteins - metabolism
Escherichia coli
Escherichia coli - genetics
Escherichia coli - metabolism
Escherichia coli Proteins
Gene Expression
membrane proteins
Membrane Transport Proteins
Molecular Sequence Data
Protein Biosynthesis
Tat translocase
TatABCE
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Summary:The Tat (twin‐arginine translocation) pathway is a Sec‐independent mechanism for translocating folded preproteins across or into the inner membrane of Escherichia coli. To study Tat translocation, we sought an in vitro translocation assay using purified inner membrane vesicles and in vitro synthesized substrate protein. While membrane vesicles derived from wild‐type cells translocate the Sec‐dependent substrate proOmpA, translocation of a Tat‐dependent substrate, SufI, was not detected. We established that in vivo overexpression of SufI can saturate the Tat translocase, and that simultaneous overexpression of TatA, B and C relieves this SufI saturation. Using membrane vesicles derived from cells overexpressing TatABC, in vitro translocation of SufI was detected. Like translocation in vivo, translocation of SufI in vitro requires TatABC, an intact membrane potential and the twin‐arginine targeting motif within the signal peptide of SufI. In contrast to Sec translocase, we find that Tat translocase does not require ATP. The development of an in vitro translocation assay is a prerequisite for further biochemical investigations of the mechanism of translocation, substrate recognition and translocase structure.
ISSN:0261-4189
1460-2075
1460-2075
DOI:10.1093/emboj/20.10.2472