| Summary: | <p>Abstract</p> <p>Background</p> <p>Although more than 100 <it>Chlamydia pneumoniae </it>hypothetical proteins have been predicted to be inclusion membrane proteins, only a few have been experimentally demonstrated to be in the inclusion membrane. Using antibodies raised with fusion proteins, we characterized four such hypothetical proteins encoded by two gene clusters (<it>Cpn0146-147 </it>and <it>Cpn0284-285</it>) in the <it>C. pneumoniae </it>genome.</p> <p>Results</p> <p>Cpn0146 and 0147 were detected in the inclusion membrane while Cpn0284 and 0285 inside inclusion and mainly associated with reticulate bodies although all four proteins contain an N-terminal bi-lobed hydrophobic region, a signature motif assigned to inclusion membrane proteins. These four hypothetical proteins were only detected in cells infected with <it>C. pneumoniae </it>but not other chlamydial species, with Cpn0147 at 6 hours and Cpn0146, 0284 & 0285 at 24 hours after infection. Cpn0146 & 147 but not Cpn0284 and 285 co-localized with a host cell endoplasmic reticulum marker, a property known to be possessed by some chlamydial inclusion membrane proteins, when expressed in the host cell cytosol via transgenes. However, the endoplasmic reticulum localization of the <it>C. pneumoniae </it>inclusion membrane proteins did not result in inhibition of the subsequent <it>C. pneumoniae </it>infection.</p> <p>Conclusion</p> <p>The hypothetical proteins Cpn0146 & 0147 were localized in the <it>C. pneumoniae </it>inclusion membrane while Cpn0284 & 0285 within the inclusion although all four were predicted to be Inc proteins, suggesting the need to experimentally characterize the predicted Inc proteins.</p>
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