Myelin basic protein (MBP) is one of the major protein constituents of myelin, along with myelin oligodendrocyte glycoprotein (MOG) and proteolipid protein (PLP), which between them make up 15% – 25% of its dry weight, the rest being mainly lipids. Myelin has an essential insulating role for nerves, allowing normal motor function, sensory function and cognition and MBP helps maintain its structure through interaction with the lipids in the myelin membrane.
Four major isoforms of MBPs exist with molecular masses of 21.5 kDa, 18.5 kDa, 17.0 kDa, and 14.0 kDa, with the most predominant being the protein of about 18.5 Kd (170 residues). The presence of MBP in the central nervous system is further complicated by the existence of several splice variants and a large number of post-translational modifications, including phosphorylation, methylation, deamidation, and citrullination.
Interest in MBP has centered on its role in demyelinating diseases, in particular, multiple sclerosis (MS). The target antigen of the autoimmune response in MS has not yet been identified though MBP is known for its autoantigenic properties in MS. Injection of purified MBP in several animal models can induce experimental autoimmune encephalitis (EAE) and MBP knockout mice (shiverer mice) exhibit decreased amounts of CNS myelination and a progressive disorder characterised by tremours, seizures, and early death.