The MS analysis of methylation sites of uL14 by Rkm1 in the in vitro methylation reaction. The uL14 was reacted with Rkm1 and SAM in the in vitro methylation reaction. (A–D) The proteins were digested with GluC (A), LysC (B), and trypsin (C) and analyzed by mass spectrometry. The ratios of methylated peptides were counted in each reaction (D).