PspA plays a key role in bacterial stress response

The phage shock protein (Psp) system was discovered in bacteria approximately 30years ago. At the time, it was identified to be a response of Escherichia coli bacteria to infection with special viruses called bacteriophages. Later it became clear that its function in protecting the cell membrane exceeds the specific response to bacteriophage infection. Osmotic stress, heat, cell toxins, or defects in the membrane envelope can also trigger the stress reaction.

"Today, we know that the Psp system is activated in response to numerous types of membrane stress. However, several molecular details still remain puzzling," explained Professor Dirk Schneider, head of the Membrane Proteins group at JGU. "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 phageshockproteinA (PspA), which has a key role in the Pspsystem. 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.