Psp Structure Observed

In a joint project, teams from Johannes Gutenberg University Mainz and Forschungszentrum Jülich, with participation of Heinrich Heine University Düsseldorf, have now discovered that a membrane protein found in bacteria has a similar structure and function as a group of proteins that are responsible for remodeling and rebuilding the cell membrane in humans. The team's research work was published in Cell.

"Today, we know that the phage shock protein (Psp) system is activated in response to numerous types of membrane stress. However, several molecular details still remain puzzling," explained lead researcher Dirk Schneider. "That's why we decided to take a closer look at core proteins of the Psp system." Together with his team, he has recently discovered how the Psp representative IM30 forms a protective carpet-like structure on a cell membrane in order to cope with membrane stress.

In their new work, the scientists scrutinized the phage shock protein A (PspA), which has a key role in the Psp system. Specifically, by using cryo-electron microscopy, it became visible how PspA forms long, spiral-shaped tubes that can enclose a biomembrane in the inner cavity. The high-resolution images now show for the very first time how PspA dissolves individual membranes locally and then reshapes them into larger units or even mediates the formation of new membrane structures.

"Thousands of PspA building blocks can be assembled to form large helical structures. Therefore, they are an ideal research object for our cryo-electron microscopic structural analysis," said collaborator Carsten Sachse. Under the microscope, the researchers were able to resolve the structure of PspA. "Under the microscope, we realized that PspA has a structure similar to ESCRT-III proteins, which our laboratory had already been working on. This came as a complete surprise and showed how important it is to elucidate protein structures in detail," said Sachse. "After billions of years, the two groups of proteins have genetically diverged so far that their similarities could only be detected based on their structure."