After their production in cells proteins can be modified by enzymes. One such modification is the so-called phosphorylation, where a phosphate residue is attached to a protein. This modification plays a role in the transmission of signals in cells, which among other things, leads to cell growth or cell division, and thus has an essential function for organisms. Malfunctions in signal transduction can lead to diseases such as cancer.
Our goal is to investigate these signaling pathways in cells and to develop new methods for this purpose. During this process, proteins from cells are cut into small fragments (peptides), resulting in peptides with and without phosphorylation. These have to be applied toan enrichment method in which phosphorylated peptides are filtered out to facilitate their identification by analytical methods (mass spectrometry).
By determining phosphorylation sites on peptides, we can then trace it back to the original protein. Here, we have developed a new method to enrich phosphopeptides. The different steps of this method are playfully depicted in a spa by Barth van Rossum on the cover of the journal ChemBioChem. In the first step (pool), phosphopeptides react specifically with a phosphorimidazolide reagent (a chemical molecule), whereas peptides without phosphorylation do not react. The reaction allows filtering out phosphopeptides from other peptides. In the next step (tanning bed), the peptides are irradiated, which removes the reagent, but leaves another phosphate on the phosphopeptide. This can be removed in the final step (sauna) by lanthanide ions (an elemental group), at elevated temperature to allow the analysis of the enriched sample.
In the future the method will be applied to identify phosphorylation sites on proteins and to contribute to the increasing understanding of signaling pathways in cells to be able to identify malfunctions and to more specifically treat diseases.
Chemoselective Labeling and Immobilization of Phosphopeptides with Phosphorimidazolide Reagents. Nathaniel W. Brown, Sandra K. Schlomach, Alan M. Marmelstein, Dorothea Fiedler. ChemBioChem, Volume 24, Issue4, February 14, 2023; e202200407.