Washington, October 8
In living organisms, the membrane that encloses the cells is incredibly delicate and flexible. Many biological activities depend on how it repairs and protects itself from harm, yet this process is still poorly understood. Researchers at Forschungszentrum Julich have now used cryo-electron microscopy to uncover intriguing new information. Known from the photosynthetic system of plants, algae, and bacteria, the membrane protein Vipp1 may generate a variety of structures that may be used as instruments to reinforce and strengthen the cell membrane when needed.
In a follow-up investigation, the scientists also managed to get fresh perspectives on the role of the associated bacterial protein PspA. Vipp1 and PspA are two molecules that have exceptional plasticity and may take on many shapes, such as rings and tubes with various diameters.
The cell membrane has numerous important functions. For instance, it protects the inside of the cell from the environment. At the same time, nutrients are absorbed through the cell membrane, waste products are excreted, and signals are transmitted between cells. Despite its central role, the cell membrane is also very sensitive. It consists of a thin layer of lipids which, although protective by themselves, are also susceptible to stress caused by physical pressure and stretching or chemical influences. Environmental factors such as UV radiation or toxins can also damage the membrane.
In plant cells, for example, intense light can severely stress and even damage the membranes in the chloroplasts, where photosynthesis takes place. Proteins such as Vipp1 are therefore essential for the survival of the cell, as they protect the membrane structures and repair them if necessary.
How exactly the mechanism works is not yet fully understood. However, thanks to the state-of-the-art cryo-electron microscopes at Julich's Ernst Ruska-Centre, the researchers have now been able to gain new insights into the interaction between Vipp1 and the cell membrane. They discovered that Vipp1 forms carpet-like structures on the cell membrane and stabilize it. In addition, they found ring complexes and tubes made of Vipp1 filled with membrane, which can possibly "pinch off" damaged membrane areas as well as connect two separate membranes.
These new findings provide new insights into the ability of the proteins Vipp1 and PspA to alter cell membranes and thus protect vital processes in the cells. These discoveries could contribute to the development of new biotechnological applications in the future, such as the production of biomaterials or the optimization of photosynthesis in plants. Vipp1 is particularly important, as it is involved in the formation and maintenance of thylakoid membranes - membranes in the chloroplasts of plant cells where the light reaction of photosynthesis takes place, i.e. the conversion of light into chemical energy. It is interesting to note that the basic mechanism is highly similar to the ESCRT-III proteins, which are also highly conserved in human cells. These proteins have remained essentially unchanged in the course of evolution, which indicates an important function. A better understanding of the structure and function of these proteins could thus lead to the development of new drugs, such as antibiotics, that target the processes in cellular membranes.