C The E139R substitution decreases the stability of UBE2S~Ub compared to WT, revealed by fluorescent scanning of a lysine discharge assay (top) and its quantification (bottom). Statistical comparison was performed using one-way ANOVA (* p ≤ 0.05, ** p ≤ 0.01, n=4 independent, technical replicates). Error bars: SEM. Data normalized to the initial timepoint of each respective E2~Ub band. 