Summer Research Description: Type three secretion systems (T3SS) are structures that are used by many Gram-negative bacteria, such as Chlamydia, in order to deliver their specific pathogenic effectors into a host’s cells. The structure of a T3SS includes translocators, which function to form a pore in the host cell, and pathogenic effectors, which can travel through this pore to cause the disease state. The goal of this study is to determine the structure and function of the CopN (gatekeeper), Scc3 (translocator chaperone), CopB (translocator) protein complex, which is hypothesized to be involved in the transition from translocator secretion to effector secretion. In order to determine the structure of this complex, CopN and Scc3 have been isolated from transformed E. coli cells. Using these proteins along with a short CopB peptide, a variety of crystals was obtained. These crystals had inconsistent nucleation sites and displayed a different space group from what was expected indicating an improper formation of the protein complex. In future experiments the whole CopB protein will be used in order to enhance protein binding due to the possibility of complementary binding sites. The determination of the structure of this protein complex could have clinical applications for the treatment of certain bacterial illnesses.