R protein. CopB2 is also secreted via a T3S mechanism when ectopically expressed in Yersinia (14), and expression studies have shown that copB2 is a midcycle gene (5). These observations have led to the hypothesis that CopB and CopB2 serve as alternative translocator proteins that could mediate translocation of effector proteins across the chlamydial inclusion membrane at different stages of devel