Is, with PLP, the most abundant protein component of the myelin membrane in the CNS. Has a role in both the formation and stabilization of this compact multilayer arrangement of bilayers. Each splice variant and charge isomer may have a specialized function in the assembly of an optimized, biochemically functional myelin membrane (By similarity). Homodimer. Cytoplasmic side of myelin. At least 5 charge isomers; C1 (the most cationic and least modified form), C2, C3, C4 and C8; are produced as a result of optional post-translational modifications, such as phosphorylation and methylation. The C-terminal arginine is partially cleaved in C2. One or both of the C-terminal arginines are partially cleaved in C3. The two C-terminal arginines are partially cleaved in C4 (PubMed:12176067). Arg-108 was found to be 25% monomethylated and 4% symmetrically dimethylated. Phosphorylated by TAOK2, VRK2, MAPK11, MAPK12, MAPK14 and MINK1. Proteolytically cleaved in B cell lysosomes by cathepsin CTSG which degrades the major immunogenic MBP epitope and prevents the activation of MBP-specific autoreactive T cells. Belongs to the myelin basic protein family.