Scientists decode how immune protein GBP1 defeats bacteria

For years, immunologists have known that a protein called GBP1 acts as a microscopic assassin inside the human body, wrapping around bacteria and parasites like a suffocating blanket until they rupture and die. What they didn't know was how it actually worked—the precise molecular choreography that allowed one protein to find, grip, and destroy an invader. Researchers at Delft University of Technology have now solved that puzzle, publishing their findings in Nature Structural & Molecular Biology, and the answer could reshape how we treat infections in people whose immune systems have failed them.

Guanylate Binding Proteins, or GBPs, are among the body's first responders to infection. They stand guard against a rogues' gallery of serious pathogens: the bacteria that cause dysentery and typhoid fever, the microbe behind tuberculosis, the organism responsible for chlamydia, and Toxoplasma gondii, which poses particular danger to pregnant women and their unborn children. Arjen Jakobi, a biophysicist leading the research, describes GBPs as the opening line of defense in the innate immune system—the part of our immunity that doesn't need to learn or remember a threat, but springs into action immediately when danger arrives.

The mechanism itself is elegant in its brutality. GBP1 proteins surround a bacterium, forming what amounts to a molecular cage. As this coat tightens around the invader, it applies pressure until the bacterium's protective membrane—the barrier that keeps it alive—ruptures. Once the membrane fails, the bacterium is exposed and vulnerable. Immune cells move in to finish the job, clearing away the debris. Tanja Kuhm, a PhD candidate in Jakobi's group and the study's lead author, describes the process with the precision of someone who has watched it happen at the molecular level.

To see this process in action, the team deployed cryo-electron microscopy, a technique that freezes biological samples at temperatures near absolute zero and images them with an electron beam. The result is a three-dimensional map of extraordinary detail—down to the scale of individual molecules. Jakobi and his colleagues could now see exactly how GBP1 proteins bind to bacterial membranes, how they assemble into a coordinated coat, and how the geometry of that coat creates the force needed to break through. Complementary experiments conducted in Sander Tans' group at the research institute AMOLF allowed the team to manipulate the system with precision, confirming their observations and filling in the remaining gaps.

The practical implications are significant. If scientists can understand precisely how GBP1 activates and deactivates, they may be able to design medications that amplify its effect—essentially turning up the volume on the body's own bacterial-fighting machinery. For people with compromised immune systems, or for infections that have proven difficult to treat with conventional antibiotics, this could open new therapeutic pathways. Jakobi notes that the research provides a foundation for that work: a clear picture of the mechanism means researchers can now think about how to manipulate it, to speed up the body's ability to clear certain infections. The next phase will be translating this molecular understanding into drugs that work in living patients—a journey that typically takes years, but one that now has a much clearer map.