Secretion of Cpn0796 from Chlamydia pneumoniae into the host cell cytoplasm by an autotransporter mechanism.
By comparison of proteome profiles of purified Chlamydia pneumoniae and whole lysates of C. pneumoniae infected HEp-2 cells, an N-terminal fragment of the previously uncharacterized chlamydial protein Cpn0796 was identified as a secreted protein. A 38 kDa cleavage product of Cpn0796 was present in infected cells, whereas only the 65 kDa full-length Cpn0796 could be detected in purified Chlamydia. Confocal immunofluorescence microscopy demonstrated that Cpn0796 was localized in the Chlamydia membrane in young inclusions. However, at 36 h post infection and later Cpn0796 was detected in the cytoplasm of C. pneumoniae infected HEp-2 and BHK cells. Furthermore, Cpn0796 was detected in the cytoplasm of infected cells in the lungs of C. pneumoniae infected C57Bl mice. When cleavage was inhibited, Cpn0796 was retained in the chlamydiae. We propose that Cpn0796 is an autotransporter the N-terminal of which is translocated to the host cell cytoplasm. This is the first example of secretion of a Chlamydia autotransporter passenger domain into the host cell cytoplasm. Cpn0796 is specific for C. pneumoniae, where five homologous proteins are encoded by clustered genes. None of these five proteins were found to be secreted.
Vandahl
Brian B S
BB
Institute of Medical Microbiology and Immunology, University of Aarhus, The Bartholin Building, DK-8000 Aarhus C, Denmark. vandahl@medmicro.au.dk
Stensballe
Allan
A
Roepstorff
Peter
P
Christiansen
Gunna
G
Birkelund
Svend
S
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002690:Chlamydia Infections / Q000382:microbiology; D016993:Chlamydophila pneumoniae / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D021381:Protein Transport; D020543:Proteome / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D002352:Carrier Proteins; D020543:Proteome