Researchers from King’s College, UK, identified a new bacterial protein that is being used to create protein nanoparticles to target anticancer drugs to tumours, according to a study published in PNAS.
The new bacterial protein, which has been named BeeR, has a similar function to actin, the most abundant protein in most human cells. In simple terms, actin molecules produce long spiral chains known as filaments, which sit in the outer membrane of cells and have many essential functions, including cell division and movement. Researchers know that bacteria have similar proteins with similar functions, but when they assessed BeeR’s 3D structure, they discovered striking differences.
“We used metagenomics data – extensive sequencing of bacterial genomes from the environment – to identify a previously unknown actin-like protein in a family of bacteria known as Verrucomicrobiota,” said Dr Julien Bergeron, Senior Lecturer in the Randall Centre for Cell & Molecular Biophysics at King’s College London. “Using the most advanced cryo-electron microscopes, we were able to determine the atomic structure of this protein, demonstrating that instead of a filament, it forms a rigid tube with a hollow cavity at its center. This is strikingly different from actin, or any of its other bacterial counterparts.”
Using advanced imaging techniques, Dr Bergeron found that in the presence of ATP, BeeR assembles into three stands that form a hollow, tubular structure. “At this time, we don’t know the function of BeeR,” adds Dr Bergeron. “Nonetheless, the identification of an actin-like protein forming a tubular structure transforms our understanding of the evolution of this critically important family of proteins.”
Through his spin-out company Prosemble, Dr. Bergeron and his team plan to use this unique structure of hollow BeeR tubes to create protein nanoparticles to deliver anticancer drugs directly to tumour sites. The team is currently testing the method in pre-clinical breast cancer models. “Not only are the BeeR structures tubular, but they also have a cavity at their centre that is big enough to contain drug molecules. Since we can easily control the assembly and disassembly of the tube with ATP, it gives us a simple method to deliver and release the drugs at the desired location,” concluded Dr Bergeron.
Bergeron J, Lale-Farjat S, Lewicka H, Parry C, & Kollman J (2025) A family of bacterial actin homologs forms a three-stranded tubular structure, Proc. Natl. Acad. Sci. U.S.A. 122 (11) e2500913122, https://doi.org/10.1073/pnas.2500913122