Determine Interaction Affinity Changes of the SUMO E1 Activating Enzymes During SUMO Activation using Quantitative FRET technology

The heterodimeric E1 complex, Aos1-Uba2, catalyzes the first adenylation activation of the SUMO1 peptide in the SUMOylation cascade. The reaction affinity and dynamics of the Aos1-Uba2 heterodimer during the first step activation have yet to be determined. The Kd for the Aos1-Uba2 interaction provides a unique perspective for the activation step of the ubiquitin-like protein conjugation cascade. Here, we report for the first time the determination of the Aos1 and Uba2 interaction dissociation constant (Kd) and kinetics using the qFRET assay. We also used the SPR method to verify the interaction Kd between Aos1 and Uba2. We also determined the kinetics changes of Aos1-Uba2 when SUMOs and ATP were added to the reaction in real time. The results showed that forming a thioester bond between SUMO1 and Uba2 increases the FRET signal, indicating that the E1 heterodimer is more stable and bound to each other in SUMO and ATP. These results suggest that the qFRET method can be used to determine protein interaction affinity changes and track real-time changes in protein conformation and dynamics changes during biochemical reactions.