Mapping the phosphoinositide-binding site on chick cofilin explains how PIP2 regulates the cofilin-actin interaction.

Cofilin plays a key role in the choreography of actin dynamics via its ability to sever actin filaments and increase the rate of monomer dissociation from pointed ends. The exact manner by which phosphoinositides bind to cofilin and inhibit its interaction with actin has proven difficult to ascertain. We determined the structure of chick cofilin and used NMR chemical shift mapping and structure-directed mutagenesis to unambiguously locate its recognition site for phosphoinositides (PIs).