title: A translocator-specific export signal establishes the translocator-effector secretion hierarchy that is important for type III secretion system function.
abstract: Type III secretion systems are used by many Gram-negative pathogens to directly deliver effector proteins into the cytoplasm of host cells. To accomplish this, bacteria secrete translocator proteins that form a pore in the host-cell membrane through which the effector proteins are then introduced into the host cell. Evidence from multiple systems indicates that the pore-forming translocator proteins are exported before effectors, but how this secretion hierarchy is established is unclear. Here we used the Pseudomonas aeruginosa translocator protein PopD as a model to identify its export signals. The N-terminal secretion signal and chaperone, PcrH, are required for export under all conditions. Two novel signals in PopD, one proximal to the chaperone binding site and one at the very C-terminus of the protein, are required for export of PopD before effector proteins. These novel export signals establish the translocator-effector secretion hierarchy, which in turn, is critical for the delivery of effectors into host cells.
authors.affiliation: Department of Molecular Biology and Microbiology, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4960, USA.
authors.forename: Amanda G
authors.initials: AG
authors.lastname: Tomalka
authors.forename: Charles M
authors.initials: CM
authors.lastname: Stopford
authors.forename: Pei-Chung
authors.initials: PC
authors.lastname: Lee
authors.forename: Arne
authors.initials: A
authors.lastname: Rietsch
mesh_terms: D058947:Bacterial Secretion Systems / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D021382:Protein Sorting Signals; D021381:Protein Transport; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*
chemical_list: D058947:Bacterial Secretion Systems; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals