title: The 'P-usher', a novel protein transporter involved in fimbrial assembly and TpsA secretion.
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 beta-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 beta-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.
authors.affiliation: UPR9027 CNRS, Systémes membranaires et pathogénicité chez Pseudomonas aeruginosa, LISM, IBSM, Marseille, France.
authors.forename: Ségolène
authors.initials: S
authors.lastname: Ruer
authors.forename: Geneviève
authors.initials: G
authors.lastname: Ball
authors.forename: Alain
authors.initials: A
authors.lastname: Filloux
authors.forename: Sophie
authors.initials: S
authors.lastname: de Bentzmann
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000494:pharmacology; D000595:Amino Acid Sequence; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008957:Models, Genetic; D018832:Molecular Chaperones / Q000378:metabolism; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D018829:Adhesins, Bacterial; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D009841:Oligonucleotides