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      The DsbA Signal Sequence Directs Efficient, Cotranslational Export of Passenger Proteins to the Escherichia coli Periplasm via the Signal Recognition Particle Pathway

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      Journal of Bacteriology

      American Society for Microbiology

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          Abstract

          The Escherichia coli cytoplasmic protein thioredoxin 1 can be efficiently exported to the periplasmic space by the signal sequence of the DsbA protein (DsbAss) but not by the signal sequence of alkaline phosphatase (PhoA) or maltose binding protein (MBP). Using mutations of the signal recognition particle (SRP) pathway, we found that DsbAss directs thioredoxin 1 to the SRP export pathway. When DsbAss is fused to MBP, MBP also is directed to the SRP pathway. We show directly that the DsbAss-promoted export of MBP is largely cotranslational, in contrast to the mode of MBP export when the native signal sequence is utilized. However, both the export of thioredoxin 1 by DsbAss and the export of DsbA itself are quite sensitive to even the slight inhibition of SecA. These results suggest that SecA may be essential for both the slow posttranslational pathway and the SRP-dependent cotranslational pathway. Finally, probably because of its rapid folding in the cytoplasm, thioredoxin provides, along with gene fusion approaches, a sensitive assay system for signal sequences that utilize the SRP pathway.

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          Author and article information

          Journal
          Journal of Bacteriology
          J. Bacteriol.
          American Society for Microbiology
          0021-9193
          1098-5530
          September 16 2003
          October 01 2003
          October 01 2003
          September 16 2003
          : 185
          : 19
          : 5706-5713
          10.1128/JB.185.19.5706-5713.2003
          193964
          13129941
          © 2003

          Molecular medicine, Neurosciences

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