Interactions between flagellar and type III secretion proteins in Chlamydia pneumoniae.
BACKGROUND
Flagellar secretion systems are utilized by a wide variety of bacteria to construct the flagellum, a conserved apparatus that allows for migration towards non-hostile, nutrient rich environments. Chlamydia pneumoniae is an obligate, intracellular pathogen whose genome contains at least three orthologs of flagellar proteins, namely FliI, FlhA and FliF, but the role of these proteins remains unknown.


RESULTS
Full length FliI, and fragments of FlhA, FliF, and FliI, were cloned and expressed as either GST or His tagged proteins in E. coli. The GST-tagged full length FliI protein was shown to possess ATPase activity, hydrolyzing ATP at a rate of 0.15 +/- .02 micromol min-1 mg-1 in a time- and dose-dependant manner. Using bacterial-2-hybrid and GST pull-down assays, the N-terminal domain of FliI was shown to interact with the cytoplasmic domain of FlhA, but not with FliF, and the cytoplasmic domain of FlhA was shown to interact with the C-terminus of FliF. The absence of other flagellar orthologs led us to explore cross-reaction of flagellar proteins with type III secretion proteins, and we found that FliI interacted with CdsL and CopN, while FlhA interacted with CdsL and Cpn0322 (YscU ortholog CdsU).


CONCLUSIONS
The specific interaction of the four orthologous flagellar proteins in C. pneumoniae suggests that they interact in vivo and, taken together with their conservation across members of the chlamydiae sps., and their interaction with T3S components, suggests a role in bacterial replication and/or intracellular survival.
Stone
Chris B
CB
M,G, DeGroote Institute for Infectious Disease Research, Faculty of Health Sciences and the Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Bulir
David C
DC
Gilchrist
Jodi D
JD
Toor
Raman K
RK
Mahony
James B
JB
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016993:Chlamydophila pneumoniae / Q000201:enzymology* / Q000235:genetics; D005978:Glutathione; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; C080688:FlhA protein, Bacteria; C075661:Flif protein, Bacteria; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C074426:FliL protein, Bacteria; D000251:Adenosine Triphosphatases; D005978:Glutathione