Bacteria use these syringes, also known as type III secretion systems (T3SS), to deliver proteins directly into the host cell's cytoplasm, hijacking cellular processes and causing disease. Understanding how bacteria build these syringes could lead to new strategies to combat bacterial infections.
In the study, published in the journal Nature Communications, the researchers used a combination of techniques, including X-ray crystallography and cryo-electron microscopy, to determine the structure of a key protein component of the T3SS, called the needle tip complex. This complex forms the tip of the syringe and plays a crucial role in puncturing the host cell membrane.
The researchers found that the needle tip complex is composed of several subunits that come together to form a ring-shaped structure. This structure is similar to the needle tip complex of other type III secretion systems, suggesting that it may be a conserved feature across different bacterial species.
The researchers also investigated how the needle tip complex interacts with the host cell membrane. They found that the complex contains a hydrophobic patch that likely inserts into the membrane, allowing the syringe to puncture the cell and deliver its virulence factors.
This research provides new insights into the structure and function of the type III secretion system, and could lead to the development of new antibiotics that target this essential virulence mechanism.
