F Autoradiograph of BiP, AMPylated in vitro by the indicated FICD derivatives, with [α-32P]-ATP as a substrate and resolved by SDS-PAGE. Proteins in the gel were visualised by Coomassie staining. A representative result of three independent experiments is shown. The graph shows the quantified relative BiP-AMP signals and SD bars generated by wild-type (wt) FICD and the indicated monomeric mutants. 