Scientists discover how innate immunity envelops bacteria

The protein GBP1 is a vital component of our body’s natural defense against pathogens. This substance fights against bacteria and parasites by enveloping them in a protein coat, but how the substance manages to do this has remained unknown until now.

Researchers from Delft University of Technology have now unraveled how this protein operates. This new knowledge, published in Nature Structural & Molecular Biology, could aid in the development of medications and therapies for individuals with weakened immune systems.

So-called Guanylate Binding Proteins (GBPs) play a crucial role in our innate immune system, explains biophysicist Arjen Jakobi, “GBPs form the first line of defense against various infectious diseases caused by bacteria and parasites. Examples of such diseases include dysentery, typhoid fever caused by Salmonella bacteria, and tuberculosis. The protein also plays a significant role in the sexually transmitted infection chlamydia as well as in toxoplasmosis, which is particularly dangerous during pregnancy and for unborn children.”

In their publication, Jakobi and his colleagues describe for the first time how the innate immune system fights against bacteria using GBP1 proteins.

“The protein surrounds bacteria by forming a sort of coat around them,” explains Tanja Kuhm, Ph.D. candidate in Jakobi’s research group and the lead author of the article. “By pulling this coat tighter, it breaks the membrane of the bacteria—the protective layer surrounding the intruder—after which immune cells can clear the infection.”

To decode the defense strategy of GBPs, the researchers examined how GBP1 proteins bind to bacterial membranes using a cryogenic electron microscope. This allowed them to see the process in great detail down to the scale of molecules.

Jakobi says, “We were able to obtain a detailed three-dimensional image of how the protein coat forms. Together with biophysical experiments conducted in Sander Tans’ research group at research institute AMOLF, which enabled us to manipulate the system precisely, we succeeded in deciphering the mechanism of the antibacterial function.”

According to Jakobi, this research helps us understand better how our body is capable of combating bacterial infections. “If we can grasp this well, and we can specifically activate or deactivate the involved proteins through medication, it may offer opportunities to speed up getting rid of certain infections.”