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J. Bacteriol. doi:10.1128/JB.01997-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Interactions Between CdsD, CdsQ and CdsL, Three Putative Chlamydophila pneumoniae Type III Secretion Proteins

M.G. DeGroote Institute for Infectious Disease Research, Faculty of Health Sciences and the Department of Pathology and Molecular Medicine, McMaster University, and the Father Sean O'Sullivan Research Centre, St. Joseph's Healthcare, Hamilton, Ontario, CANADA

^* To whom correspondence should be addressed. Email: mahonyj{at}mcmaster.ca.

	Abstract

Chlamydophila pneumoniae is a gram negative obligate intracellular bacterial pathogen that causes pneumonia, bronchitis and may contribute to atherosclerosis. The developmental cycle of C. pneumoniae includes a morphological transition from an infectious extracellular elementary body (EB) to a non-infectious intracellular reticulate body (RB) that divides by binary fission. The C. pneumoniae genome encodes a type III secretion (T3S) apparatus that may be used to infect eukaryotic cells and to evade the host immune response. In the present study Cpn0712 (CdsD), Cpn0704 (CdsQ) and Cpn0826 (CdsL), three C. pneumoniae genes encoding Yersiniae type III secretion YscD, YscQ and YscL homologs, respectively, were cloned and expressed as histidine- and GST-tagged proteins in E. coli. Purified recombinant proteins were used to raise hyper-immune polyclonal antiserum, and were used in GST pull-down and co-purification assays to identify protein-protein interactions. CdsD was detected in both EB and RB lysates by Western blot, and immunofluorescent staining demonstrated the presence of CdsD within inclusions. Triton X-114 solubilization and phase separation of chlamydial EB proteins indicated that CdsD partitions with cytoplasmic proteins, suggesting it is not an integral membrane protein. GST pull-down assays indicated that recombinant CdsD interacts with CdsQ and CdsL, and co-purification assays with chlamydial lysates confirmed that native CdsD interacts with CdsQ and CdsL. To the best of our knowledge this is the first report demonstrating interactions between YscD, YscQ and YscL homologs of bacterial T3S systems. These novel protein interactions may play important roles in the assembly or function of the chlamydial T3S apparatus.

This article has been cited by other articles:

• Stone, C. B., Johnson, D. L., Bulir, D. C., Gilchrist, J. D., Mahony, J. B. (2008). Characterization of the Putative Type III Secretion ATPase CdsN (Cpn0707) of Chlamydophila pneumoniae. J. Bacteriol. 190: 6580-6588 [Abstract] [Full Text]