This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yang, Y. B. Articles by Tai, P. C. Search for Related Content PubMed PubMed Citation Articles by Yang, Y. B. Articles by Tai, P. C.

 Previous Article  |  Next Article 

J. Bacteriol., Dec 1997, 7386-7393, Vol 179, No. 23
Copyright © 1997, American Society for Microbiology

Differential translocation of protein precursors across SecY-deficient membranes of Escherichia coli: SecY is not obligatorily required for translocation of certain secretory proteins in vitro

YB Yang, J Lian and PC Tai
Department of Biology, Georgia State University, Atlanta 30303, USA.

SecY, a component of the protein translocation system in Escherichia coli, was depleted at a nonpermissive temperature in a strain which had a temperature-sensitive polar effect on the expression of its secY. Membrane vesicles prepared from these cells, when grown at the nonpermissive temperature, contained about 5% SecY and similarly low levels of SecG. As expected, translocation of alkaline phosphatase precursors across these SecY-deficient membranes was severely impaired and appeared to be directly related to the decrease of SecY amounts. However, despite such a dramatic reduction in SecY and SecG levels, these membranes exhibited 50 to 70% of the wild-type translocation activity, including the processing of the signal peptide, of OmpA precursor (proOmpA). This translocation activity in SecY-deficient membranes was still SecA and ATP dependent and was not unique to proOmpA, as lipoprotein and lambda receptor protein precursors were also transported efficiently. Membranes that were reconstituted from these SecY-depleted membranes contained undetectable amounts of SecY yet were also shown to possess substantial translocation activity for proOmpA. These results indicate that the requirement of SecY for translocation is not obligatory for all secretory proteins and may depend on the nature of precursors. Consequently, it is unlikely that SecY is the essential core channel through which all precursors traverse across membranes; rather, SecY probably contributes to efficiency and specificity.

This article has been cited by other articles:

• Doerrler, W. T., Raetz, C. R. H. (2005). Loss of Outer Membrane Proteins without Inhibition of Lipid Export in an Escherichia coli YaeT Mutant. J. Biol. Chem. 280: 27679-27687 [Abstract] [Full Text]  
• Wang, H.-W., Chen, Y., Yang, H., Chen, X., Duan, M.-X., Tai, P. C., Sui, S.-F. (2003). Ring-like pore structures of SecA: Implication for bacterial protein-conducting channels. Proc. Natl. Acad. Sci. USA 100: 4221-4226 [Abstract] [Full Text]  
• Qi, H.-Y., Hyndman, J. B., Bernstein, H. D. (2002). DnaK Promotes the Selective Export of Outer Membrane Protein Precursors in SecA-deficient Escherichia coli. J. Biol. Chem. 277: 51077-51083 [Abstract] [Full Text]  
• Berlyn, M. K. B. (1998). Linkage Map of Escherichia coli K-12, Edition 10: The Traditional Map. Microbiol. Mol. Biol. Rev. 62: 814-984 [Abstract] [Full Text]  
• Chen, X., Brown, T., Tai, P. C. (1998). Identification and Characterization of Protease-Resistant SecA Fragments: SecA Has Two Membrane-Integral Forms. J. Bacteriol. 180: 527-537 [Abstract] [Full Text]