Microtubules are the ubiquitous cytoskeletal structural components that are involved in intracellular transport. They are composed of tubulin and microtubule-associated proteins(MAPs). MAP1 is one of the major neuronal MAPs as well as being the largest(350KD). MAPs include MAP1A, MAP1B , and MAP2. MAP1a is a single-copy gene spanning 10.5 kb. MAP1a coding sequence is contained in five exons. MAP1B is encoded as a polyprotein that is processed to form a complex N-terminal microtubule-binding domain.