A zyxin head–tail interaction regulates zyxin–VASP complex formation

Zyxin is an adhesion protein that regulates actin assembly by binding to VASP family members through N-terminal proline-rich motifs. Evidence suggests that zyxin’s C-terminal LIM domains function as a negative regulator of zyxin–VASP complexes. Zyxin LIM domains access to binding partners is negatively regulated by an unknown mechanism. One possibility is that zyxin LIM domains mediate a head–tail interaction, blocking interactions with other proteins. Such a mechanism might prevent both zyxin–VASP complexes activity and LIM domain access. In this report, the effect of LIM domains on zyxin–VASP complex assembly is defined. We find that zyxin LIM domains associate with zyxin’s VASP binding sites, preventing zyxin from binding to PKA-phosphorylated VASP. Unphosphorylated VASP overcomes the head–tail interaction, a result of a direct interaction with the LIM domain region. Zyxin, like a growing number of actin regulators, is controlled by intramolecular interactions.