Protein arginine methyltransferase 6 is a novel substrate of protein arginine methyltransferase 1

Figure 4 Liquid chromatography with tandem mass spectrometry analysis of the methylation sites on protein arginine methyltransferase 6. A: 5.5 M protein arginine methyltransferase (PRMT) 6 and 200 M S-adenosyl methionine were incubated with 1 M PRMT1 at 30 ℃ for 3 h in the reaction buffer. The methylated PRMT6 band was separated by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, cut from the gel, washed and vacuum-dried. The sample was sent to UAB proteomics and mass spectrometry facility (Birmingham, AL 35294) for in-gel digestion and liquid chromatography-tandem mass spectrometry (MS/MS) detection. Tandem MS spectra showing the arginine-dimethylated peptides; B: PRMT6 protein sequence coverage (yellow) and the modified residues (green) detected by tandem MS analysis. Green "C" is with carboamidomethylation, and green "M" is with oxidation.