title: The polypeptide transport-associated (POTRA) domains of TpsB transporters determine the system specificity of two-partner secretion systems.
abstract: The two-partner secretion (TPS) systems of Gram-negative bacteria secrete large TpsA exoproteins by a dedicated TpsB transporter in the outer membrane. TpsBs contain an N-terminal module located in the periplasm that includes two polypeptide transport-associated (POTRA) domains. These are thought to initiate secretion of a TpsA by binding its N-terminal secretion signal, called the TPS domain. Neisseria meningitidis encodes up to five TpsA proteins that are secreted via only two TpsB transporters: TpsB1 and TpsB2. Of these two, the TpsB2 recognizes the TPS domains of all TpsAs, despite their sequence diversity. By contrast, the TpsB1 shows a limited recognition of a TPS domain that is shared by two TpsAs. The difference in substrate specificity of the TpsBs enabled us to investigate the role of the POTRA domains in the selection of TPS domains. We tested secretion of TPS domains or full-length TpsAs by TpsB mutants with deleted, duplicated, and exchanged POTRA domains. Exchanging the two POTRA domains of a TpsB resulted in a switch in specificity. Furthermore, exchanging a single POTRA domain showed that each of the two domains contributed to the cargo selection. Remarkably, the order of the POTRA domains could be reversed without affecting substrate selection, but this aberrant order did result in an alternatively processed secretion product. Our results suggest that secretion of a TpsA is initiated by engaging both POTRA domains of a TpsB transporter and that these select the cognate TpsAs for secretion.
authors.affiliation: From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and.
authors.forename: Sadeeq
authors.initials: S
authors.lastname: ur Rahman
authors.affiliation: the Section of Molecular Microbiology, Department of Biology, Utrecht University, 3584 CH Utrecht, The Netherlands.
authors.forename: Jesús
authors.initials: J
authors.lastname: Arenas
authors.affiliation: From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and.
authors.forename: Hülya
authors.initials: H
authors.lastname: Öztürk
authors.affiliation: From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and.
authors.forename: Nicole
authors.initials: N
authors.lastname: Dekker
authors.affiliation: From the Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and j.p.van.ulsen@vu.nl.
authors.forename: Peter
authors.initials: P
authors.lastname: van Ulsen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D009345:Neisseria meningitidis / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D002352:Carrier Proteins
keywords: Bacterial Pathogenesis; Membrane Protein; Membrane Transport; Omp85 Protein Family; POTRA Domains; Protein Secretion; Two-partner Secretion System; Virulence Factor