The obligate intracellular bacterium Chlamydia trachomatis causes substantial morbidity in the US and
worldwide. A C. trachomatis effector called Tarp for translocated actin recruiting protein is a candidate
virulence factor. Tarp is tyrosine phosphorylated by a host cell kinase and is associated with actin recruitment
during C. trachomatis entry. All reference and clinical isolates of Chlamydiae species examined to date harbor
the tarP gene. We have identified and biochemically characterized four Tarp protein domains including: i) a
phosphorylation domain ii) a proline rich oligomerization domain iii) a G-actin binding and nucleating domain,
and iv) two F-actin binding and bundling domains. We hypothesize that specific Tarp domains are required
for bacterial entry and/or chlamydial development. We will test this hypothesis by: 1) examining the
mechanics of Tarp mediated actin bundles, 2) analyzing C. trachomatis tarp mutants and complements that
express Tarp domain deletions for chlamydial invasion of host cells and development and 3). Investigate the
requirement for tarP in a mouse infection model. Elucidation of the molecular mechanisms employed by C.
trachomatis to initiate a successful infection may provide clues that can be applied to novel therapeutic
interventions for this prolific pathogen.