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; self-associates in the presence of lysolipid. Cytoplasmic side of myelin. Found in both the central and the peripheral nervous system. At least 6 charge isomers; C1 (the most cationic and least modified form), C2, C3, C4, C5 and C6 (the least cationic form); are produced as a result of optional post-translational modifications, such as phosphorylation of serine or threonine residues, deamidation of glutamine or asparagine residues, citrullination and methylation of arginine residues. 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.