Structural overview of the bacterial injectisome

The bacterial injectisome is a specialized protein-export system utilized by many pathogenic Gram-negative bacteria for the delivery of virulence proteins into the hosts they infect. This needle-like molecular nanomachine comprises >20 proteins creating a continuous passage from bacterial to host cytoplasm. The last few years have witnessed significant progress in our understanding of the structure of the injectisome with important contributions from X-ray crystallography, NMR and EM. This review will present the current state of the structure of the injectisome with particular focus on the molecular structures of individual components and how these assemble together in a functioning T3SS.