Many disease-causing bacteria, such as Yersinia, Salmonella, Shigella, and Chlamydia make use of a dedicated protein transport system to transmit pathogenic proteins to host cells. These so-called type-3 secretion systems (T3SS) consist of hollow pin-like structures on the outer shell of the bacteria. Virulence proteins that are exported through this structure are transported into host cells via an unknown mechanism.
The mechanism for this transport has previously been proposed to be occurring by injection via the pin-like structure directly from the inner part of the bacterium into the cytoplasma of the host cell. These researchers at Umeå University have now shown that virulence proteins exist on the outside of the bacterium before it has bound to the host cell and that these proteins can be transported into the host cell via a bacteria-associated protein complex. These pioneering findings are a major breakthrough in our understanding of T3SS-dependent bacteria and also open new avenues for developing antibiotics that are more specific to this type of bacteria.
In modern medical research scientists are looking for new methods for delivering proteins into cancer cells. These findings may facilitate the development of such systems by making use of the T3SS protein complex.