< Barbara successfully completed her PhD
Tuesday, 10/26/2021

Fascination protein-protein interactions

Lights. Camera. Interaction.


„You never walk alone“ is a beautiful catch phrase equally relevant for social communities as well as the subcellular organization at the molecular level. Very much like best friends also proteins, cellular micromachines, come in close contact and team up for a shared mission. For example, most processes vital to life such as replication of DNA, energy production by mitochondria, movement of muscles, or the release of hormones like insulin rely on the interactions of different proteins.

Fascinated by the output that originates from the teamwork of proteins, our lab established a method to track and measure individual protein-protein interactions in living cells. We focused on the protein translocase of the endoplasmic reticulum, a multimeric protein complex that is necessary for the transport of hundreds of other proteins including the aforementioned hormone insulin. While the interactions between subunits of the protein translocase have been addressed by biochemical co-purification methods or structural X-ray crystallography before, we managed to detect and modulate those interactions for the first time in living cells. In addition, we identified interactions of other membrane proteins of the endoplasmic reticulum that have not been shown in mammalian cells before.

The principle of the assay relies on a molecular lightbulb called luciferase. The clue, this lightbulb can be disassembled into the bulb and the glow filament that are individually attached to proteins of interest using standardized molecular biological methods. If those fusion proteins interact, the bulb and glow filament are brought together and emit light that can be detected by a camera. Thus, like all celebrated movie stars our subunits of the protein translocase were just waiting for the famous words “Lights. Camera. (Inter)action.” of the movie director and first author Mark Sicking. Using the expertise of the team’s chemist, Prof. Dr. Martin Jung, different types of glow filaments (biomimetic peptides) were designed that allowed us to determine the presence and localization of the bulb part within cells. Overall, this work laid the cornerstone for further studies that will address the dynamic behavior of protein-protein interactions in cellular systems. Further information about our team can be found at https://www.molmed-saarland.eu/team-lang/.

(Text/Foto by Sven Lang; from left to right: Sven Lang, Mark Sicking, Martin Jung)