Secretion of LamB-LacZ by the signal recognition particle pathway of Escherichia coli

Christina Wilson Bowers, Fion Lau, Thomas J. Silhavy

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60 Scopus citations


LamB-LacZ fusion proteins have classically been used in studies of the general secretion pathway of Escherichia coli. Here we describe how increasing signal sequence hydrophobicity routes LamB-LacZ Hyb42-1 to the signal recognition particle (SRP) pathway. Secretion of this hydrophobic fusion variant (H*LamB-LacZ) was reduced in the absence of fully functional Ffh and Ffs, and the translocator jamming caused by Hyb42-1 was prevented by efficient delivery of the fusion to the periplasm. Finally, we found that in the absence of the ribosome-associated chaperone, trigger factor (Tig), LamB-LacZ localized to the periplasm in a SecA-dependent, SRP-independent fashion. Collectively, our results provide compelling in vivo evidence that there is an SRP-dependent cotranslational targeting mechanism in E. coli and argue against a role for trigger factor in pathway discrimination.

Original languageEnglish (US)
Pages (from-to)5697-5705
Number of pages9
JournalJournal of bacteriology
Issue number19
StatePublished - Oct 2003

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Microbiology


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