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Journal of Bacteriology, August 2009, p. 5169-5179, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00458-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Role of Periplasmic Chaperones and BamA (YaeT/Omp85) in Folding and Secretion of Intimin from Enteropathogenic Escherichia coli Strains{triangledown} ,{dagger}

Gustavo Bodelón, Elvira Marín, and Luis Ángel Fernández*

Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, 28049 Madrid, Spain

Received 3 April 2009/ Accepted 3 June 2009

Intimin is a bacterial adhesin located on the surface of enteropathogenic Escherichia coli and other related bacteria that is believed to self-translocate across the outer membrane (OM), and therefore it has been regarded as a member of the type V secretion system (T5SS), which includes classical autotransporters (ATs). However, intimin has few structural similarities to classical ATs and an opposite topology with an OM-embedded N region and a secreted C region. Since the actual secretion mechanism of intimin is unknown, we investigated intimin biogenesis by analyzing its requirement of periplasmic chaperones (DsbA, SurA, Skp, and DegP) and of OM protein BamA (YaeT/Omp85) for folding, OM insertion, and translocation. Using full-length and truncated intimin polypeptides, we demonstrate that DsbA catalyzes the formation of a disulfide bond in the D3 lectin-like domain of intimin in the periplasm, indicating that this secreted C-terminal domain is at least partially folded prior to its translocation across the OM. We also show that SurA chaperone plays the major role for periplasmic transport and folding of the N region of intimin, whereas the parallel pathway made by Skp and DegP chaperones plays a secondary role in this process. Further, we demonstrate that BamA is essential for the insertion of the N region of intimin in the OM and that the protease activity of DegP participates in the degradation of misfolded intimin. The significance of these findings for a BamA-dependent secretion mechanism of intimin is discussed in the context of T5SSs.

* Corresponding author. Mailing address: Centro Nacional de Biotecnología-CSIC, Campus de Cantoblanco, Madrid 28049, Spain. Phone: 34 91 585 48 54. Fax: 34 91 585 45 06. E-mail: lafdez{at}cnb.csic.es

{triangledown} Published ahead of print on 12 June 2009.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, August 2009, p. 5169-5179, Vol. 191, No. 16
0021-9193/09/$08.00+0     doi:10.1128/JB.00458-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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