SDS–PAGE analysis of CTC.445.2d labelling with TAMRA-R NGL H. Reactions were run in 100 mM HEPES buffer, pH 8, containing 50 µM protein (either KL-tagged or a variant where the Lys–Leu sequence was mutated to Ala–Leu), 1 mM TAMRA-R NGL H, 1 mM NiSO 4 and 1 µM Oa AEP1 for the indicated time points at 25 °C. The samples run on SDS–PAGE were also analysed by ESI-MS (Extended Data Fig. 7 ).
