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. Additional isoforms seem to exist. In the optic lobe, first detected at embryonic day 14. Expression strongly increases between embryonic days 16 and 18, reaches a maximum at postnatal day 1, and then declines again to the adult level. Several charge isomers 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. Chicken MBP contains 4 charge components denoted as C1, C2, C3 and C8. C1 lacks any phosphorylation sites, whereas C2 and C3 contain respectively 10 and 8 phosphorylation sites and arginine residues modified to citrulline. All three charge components contain deamidated glutamines and asparagine, and a methylated arginine. Major isoform. Belongs to the myelin basic protein family.