Twf-C and ADF/cofilin bind G-actin through a conserved mechanism. (A) Structure of the Twf-C–G-actin complex and (B) a model of yeast cofilin (Fedorov et al., 1997) bound to G-actin in the same orientation show that both proteins use a similar binding surface for G-actin. Residues shown to be important for G-actin binding by mutagenesis in Twf-C and yeast cofilin are displayed as magenta sticks, and residues important for F-actin interactions in yeast cofilin are shown in orange.