The research team, led by the HFSP Awardee Julien Bergeron, King’s College London, UK, identified a previously unknown protein in a family of bacteria found in soil and the human gut microbiome. BeeR, as the scientists named it, has a similar function to actin – the most abundant protein in most human cells. In the presence of a chemical called ATP, actin molecules can join into long spiral chains known as filaments. The filaments sit in the outer membrane of cells and have many important functions, including helping cells to maintain their shape, divide, and move. Actin can also break down ATP, which triggers the filaments to disassemble.
Bacteria have similar proteins to actin that form filaments in the presence of ATP and help to control cell shape and division. However, when studying BeeR, the researchers discovered one striking difference between it and other actin-like bacterial proteins – its structure.
Julien Bergeron 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. By using the most advanced cryo-electron microscopes, the HFSP Grantee and team 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.
The research was recently published in PNAS with a complete description of the unique 3D structure of the BeeR protein. Identifying an actin-like protein forming a tubular structure transforms the understanding of the evolution of this critically important family of proteins, opening new ways to develop cancer drug delivery systems that can target drugs to tumor sites.