MAPMODULIN - A POSSIBLE MODULATOR OF THE INTERACTION OF MICROTUBULE-ASSOCIATED PROTEINS WITH MICROTUBULES

We have purified and characterized a 31-kDa protein named mapmodulin t hat binds to the microtubule-associated proteins (MAPs) MAP2, MAP4, an d tau. Mapmodulin binds free MAPs in strong preference to microtubule- associated MAPs, and appears to do so via the MAP's tubulin-binding do main, Mapmodulin inhibits the initial rate of MAP2 binding to microtub ules, a property that may allow mapmodulin to displace MAPs from the p ath of organelles translocating along microtubules. In support of this possibility, mapmodulin stimulates the microtubule- and dynein-depend ent localization of Golgi complexes in semi intact CHO cells, To our k nowledge, mapmodulin represents the first example of a protein that ca n bind and potentially regulate multiple MAP proteins.