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A novel Sec‐independent periplasmic protein translocation pathway in Escherichia coli
Author(s) -
Santini ClaireLise,
Ize Bérengère,
Chanal Angélique,
Müller Matthias,
Giordano Gérard,
Wu LongFei
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.1.101
Subject(s) - biology , periplasmic space , escherichia coli proteins , escherichia coli , chromosomal translocation , bacterial protein , microbiology and biotechnology , computational biology , genetics , bacteria , gene
The trimethylamine N ‐oxide (TMAO) reductase of Escherichia coli is a soluble periplasmic molybdoenzyme. The precursor of this enzyme possesses a cleavable N‐terminal signal sequence which contains a twin‐arginine motif. By using various moa , mob and mod mutants defective in different steps of molybdocofactor biosynthesis, we demonstrate that acquisition of the molybdocofactor in the cytoplasm is a prerequisite for the translocation of the TMAO reductase. The activation and translocation of the TMAO reductase precursor are post‐translational processes, and activation is dissociable from translocation. The export of the TMAO reductase is driven mainly by the proton motive force, whereas sodium azide exhibits a limited effect on the export. The most intriguing observation is that translocation of the TMAO reductase across the cytoplasmic membrane is independent of the SecY, SecE, SecA and SecB proteins. Depletion of Ffh, a core component of the signal recognition particle of E.coli , appears to have a slight effect on the export of the TMAO reductase. These results strongly suggest that the translocation of the molybdoenzyme TMAO reductase into the periplasm uses a mechanism fundamentally different from general protein translocation.