Article
- The EMBO Journal (2008) 27, 2669 - 2680
- doi:10.1038/emboj.2008.197
Published online: 2 October 2008
Subject Categories:
The 'P-usher', a novel protein transporter involved in fimbrial assembly and TpsA secretion
Ségolène Ruer1, Geneviève Ball1, Alain Filloux1,2,3 and Sophie de Bentzmann1
- UPR9027 CNRS, Systémes membranaires et pathogénicité chez Pseudomonas aeruginosa, LISM, IBSM, Marseille, France
- Division of Cell and Molecular Microbiology, CMMI, Imperial College London, London, UK
- Present address: Division of Cell and Molecular Biology, CMMI, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
Correspondence to:
Alain Filloux, Division of Cell and Molecular Biology, CMMI, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. Tel.: +44 0 2075 949 651; Fax: +44 0 2075 943 069; E-mail: a.filloux@imperial.ac.uk
Sophie de Bentzmann, UPR9027 CNRS, LISM, IBSM, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France. Tel.: +33 491 164 125; Fax: +33 491 712 124; E-mail: bentzman@ibsm.cnrs-mrs.fr
Received 7 March 2008; Accepted 5 September 2008
Abstract
We identified a new bacterial transporter, the Pseudomonas aeruginosa CupB3 protein, which is an outer membrane usher involved in pili assembly. In CupB3, the usher domain has fused during evolution with a POTRA (polypeptide-transport-associated)-like domain found in TpsB transporters of two-partner secretion systems. In TpsBs, the POTRA captures the TpsA passenger, which is then transported across the outer membrane through the TpsB 
-barrel. We named CupB3 a 'P-usher' for POTRA-like domain-containing usher. We showed that CupB3 assembles CupB1 fimbrial subunits into pili and secretes CupB5, a TpsA-like protein. The CupB3 usher domain has the function of a TpsB -barrel in CupB5 translocation. We revealed that the POTRA-like domain is neither essential for CupB1 fimbriae assembly nor for cell surface exposition of CupB5, but is crucial to coordinate bona fide transport of CupB1 and CupB5 through the usher domain. The P-usher defines a novel transport pathway involving a molecular machine made with old spare parts.
Keywords:
- chaperone–usher pathway,
- fimbriae,
- POTRA,
- Pseudomonas,
- type Vb secretion
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