title: The Type III Secretion System-Related CPn0809 from Chlamydia pneumoniae.
abstract: Chlamydia pneumoniae is an intracellular Gram-negative bacterium that possesses a type III secretion system (T3SS), which enables the pathogen to deliver, in a single step, effector proteins for modulation of host-cell functions into the human host cell cytosol to establish a unique intracellular niche for replication. The translocon proteins located at the top of the T3SS needle filament are essential for its function, as they form pores in the host-cell membrane. Interestingly, unlike other Gram-negative bacteria, C. pneumoniae has two putative translocon operons, named LcrH_1 and LcrH_2. However, little is known about chlamydial translocon proteins. In this study, we analyzed CPn0809, one of the putative hydrophobic translocators encoded by the LcrH_1 operon, and identified an 'SseC-like family' domain characteristic of T3S translocators. Using bright-field and confocal microscopy, we found that CPn0809 is associated with EBs during early and very late phases of a C. pneumoniae infection. Furthermore, CPn0809 forms oligomers, and interacts with the T3SS chaperone LcrH_1, via its N-terminal segment. Moreover, expression of full-length CPn0809 in the heterologous host Escherichia coli causes a grave cytotoxic effect that leads to cell death. Taken together, our data indicate that CPn0809 likely represents one of the translocon proteins of the C. pneumoniae T3SS, and possibly plays a role in the translocation of effector proteins in the early stages of infection.
authors.affiliation: Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: Astrid C
authors.initials: AC
authors.lastname: Engel
authors.affiliation: Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: Frauke
authors.initials: F
authors.lastname: Herbst
authors.affiliation: Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Kerres
authors.affiliation: Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: Jan N
authors.initials: JN
authors.lastname: Galle
authors.affiliation: Lehrstuhl für Funktionelle Genomforschung der Mikroorganismen, Heinrich-Heine-Universität, Düsseldorf, Germany.
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Hegemann
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D023521:Chlamydophila Infections / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D016993:Chlamydophila pneumoniae / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D009876:Operon; D054730:Protein Interaction Domains and Motifs; D000069296:Type III Secretion Systems / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D000069296:Type III Secretion Systems