MAP1a (MAP1A) and MAP1b (MAP1B) are the two major members of the MAP1 family. These two proteins are high molecular weight. They bind to microtubules through charge interactions, a different mechanism to many other MAPs. While the C termini of these MAPs bind the microtubules, the N termini bind other parts of the cytoskeleton or the plasma membrane to control spacing of the microtubule within the cell. Members of the MAP1 family are found in the axons and dendrites of nerve cells.
Another member of this family is MAP1S, which has a low molecular-weight. MAP1S has been found to regulate cell division and cell death