Myelin basic protein (MBP) is the second most abundant protein in central nervous system (CNS) myelin: it comprises 30% of the total protein and about 10% of the dry weight of myelin. It is the only structural protein found so far to be essential for formation of CNS myelin, and has been called the executive molecule of myelin. MBP can interact with a number of polyanionic proteins including actin, tubulin, calmodulin, and clathrin, and negatively charged lipids, and acquires structure on binding to them. It may act as a membrane actin-binding protein, which might allow it to participate in transmission of extracellular signals to the cytoskeleton in oligodendrocytes and tight junctions in myelin. MBP may be applicable as a marker for oligodendrogliomas.