Interaction of Actin Filaments with Microtubules Is Mediated by Microtubule‐Associated Proteins and Regulated by Phosphorylationa

Abstract
We have reconstituted high viscosity networks of actin filaments and microtubules from purified actin, tubulin, and MAPs. MAP-2 can effectively cross-link actin filaments and microtubules, presumably because a low affinity actin binding site is available even when it is bound tightly to microtubules. Phosphorylation of MAP-2 inhibits cross-linking of actin filaments and microtubules. Tau is not an effective cross-linker of actin and microtubules even though it can interact with each polymer individually.