The type-III secretion system (T3SS) is an export machine used by pathogenic Gram-negative bacteria to deliver proteins straight into the eukaryotic cytosol with the aim to subvert the host cell defense. After the discovery of T3S in 1990, significant progress has been made in the understanding of its structure, assembly and function. The basic structure consisting of the membrane-embedded basal body, the needle and the tip structure has been analyzed in more detail. The composition of several structural components has been determined and important insights into the assembly process have been gained. The relationship between the T3SS of pathogenic bacteria and the flagellum has been noted. Besides the structural similarities, the assembly of these two nanomachines shows some commonalities, for example the length control of external structures such as the T3 needle and the flagellar hook. The T3SS also includes the pore forming translocator proteins, effector proteins and a set of specific chaperones. A recent review on the type-III secretion system focuses on the structure and assembly of this fascinating nanomachine.

from Sorg and Cornelis in Bacterial Secreted Proteins

Further reading:

1. Bacterial Secreted Proteins: Secretory Mechanisms and Role in Pathogenesis
2. Microbiology Books

Labels: bacteria, protein, protein secretion, proteins