Movie S1.

Morphing from G to F-actin, overall view. Actin subdomains 1 and 2, light blue ribbons. Actin subdomains 3 and 4, yellow ribbons. Actin subdomains 1 and 3 interface α-helix, cyan cartoon. ATP, sticks. Magnesium, grey sphere. The MD initial model was used for G-actin. For F-actin, a typical snapshot of an MD frame bearing all the conditions from Fig. 4E was selected. The LSQMAN software package was used to generate the morphs (http://xray.bmc.uu.se/usf/).