This protein may function to maintain proper structure of myelin. Cytoplasmic side of myelin. Several charge isomers are produced as a result of optional post-translational modifications, such as phosphorylation, deamidation and citrullination. Dogfish MBP contains four major components designated as C1, C2, C3 and C8. C1 and C3, but not C2 are phosphorylated at either Ser-121 or Ser-122; C2 is phosphorylated at 2 or 3 sites among Ser-135, Ser-139 and Ser-140. Hydroxyproline and citrulline are present but were not identified in either C1, C2 or C3, which suggests their presence in C8. Belongs to the myelin basic protein family.