B-C Dimer interface mutants both AMPylate and deAMPylate BiP. Shown are representative autoradiographs of thin layer chromatography (TLC) plates revealing AMP produced from reactions containing [α-32P]-ATP and the indicated FICD enzymes in the presence or absence of the co-substrate BiP (arrow indicates direction of nucleotide migration). The radioactive signals were quantified and the AMP signals were normalised to the total nucleotide signal in each sample. Plotted below are mean values ± SD from at least three independent experiments. Unpaired t-tests were performed. 