Several charge isomers of MBP; C1 (the most cationic, least modified, and most abundant form), C2, C3, C4, C5, C6, C7, C8-A and C8-B (the least cationic form); are produced as a result of optional PTM, such as phosphorylation, deamidation of glutamine or asparagine, arginine citrullination and methylation. C8-A and C8-B contain each two mass isoforms termed C8-A(H), C8-A(L), C8-B(H) and C8-B(L), (H) standing for higher and (L) for lower molecular weight. C3, C4 and C5 are phosphorylated. The ratio of methylated arginine residues decreases during aging, making the protein more cationic.; The N-terminal alanine is acetylated (isoform 3, isoform 4, isoform 5 and isoform 6).; Arg-241 was found to be 6% monomethylated and 60% symmetrically dimethylated.; Phosphorylated by TAOK2, VRK2, MAPK11, MAPK12, MAPK14 and MINK1.