Crosslinking assays. Purified proteins were incubated with EGS for 30 min at 25°C. After the treatment, samples were analyzed by SDS-PAGE followed by Coomassie staining. GST and ferredoxin were used as positive and negative controls of oligomerization, respectively. All proteins were at 25 μM, and the fold excess of EGS used in each case is detailed on top. Molecular weights are depicted on the left of each gel.