Molecular mechanisms of membrane protein targeting and folding have been extensively investigated over the last decade. Ribosome targeting to the membrane translocon represents an early stage of membrane protein biogenesis and is facilitated by the signal recognition particle (SRP).
Here, the group of Roland Beckmann from the Gene Center in Munich established MicroScale Thermophoresis (MST) to analyze interactions between bacterial SRP and translating ribosomes. They demonstrate that assembly of the ribosome:SRP complex can be monitored using fluorescently-labeled ribosomes confirming that the method is capable of resolving the complex assembly between two large macromolecules.
The measured affinity for ribosome:SRP at low nanomolar scale was in agreement with previous biophysical studies. Importantly, structural modifications in the ribosome and SRP, however, altered the binding affinity. Therefore, the MST method provides opportunities for rapid screening of ribosome:ligand interactions for future structural studies.