Localization and Characterization of GTP-Binding Protein CT703 in the <Emphasis Type="Italic">Chlamydia trachomatis</Emphasis>-Infected Cells

To localize and characterize the GTP-binding protein encoded by the chlamydial ORF CT703 in the Chlamydia trachomatis-infected cells, the gene coding for CT703 in the Chlamydia trachomatis serovar L2 genome was cloned into the prokaryotic expression vector pGEX and expressed as GST fusion protein in the E. coli BL21 strain. The GST-CT703 fusion protein was purified and used to raise antigen-specific antibodies. Using the anti-fusion protein antibodies, we localized the endogenous CT703 protein inside the chlamydial inclusion using an indirect immunofluorescence assay (IFA). We also detected a significantly decreased level of CT703 in cultures that were induced to undergo persistent infection. These observations suggest that CT703 may be an important regulator for promoting chlamydial productive infection.