Purified ZPR1 protein was incubated with purified NleE at 37℃ in 30 µL of methylation buffer (50 mM Tris-HCl pH 7.5, 150 mM NaCl, 5 mM DTT, 0.1% NP-40 and 0.8 mM S-Adenosyl methionine) for 30 min.