E Fluorescent scans (top) and quantification (bottom) of a *LRLRGG peptide transfer assay comparing UBE2S WT and ER/ER reveals no significant difference through an unpaired Welch's t-test (n=3 independent, technical replicates). Error bars: SEM. Data normalized to the maximal *LRLRGG-Ub formation by WT UBE2S. 