Movie 3.

Sub-tomogram averages of long and short-repeat Factin filaments within growth cones. 3D sub-tomogram averages calculated from volumes of long and short-repeat Factin and fitted models of F-actin (PDB: 7BT7, (Kumari et al., 2020)) or F-actin-cofilin (PDB: 3JOS, (Galkin et al., 2011)), as indicated. The video starts with the F-actin model fitted into the long-repeat F-actin sub-tomogram average, showing a good match. The F-actin model is then swapped for the F-actin-cofilin model, that shows a poor match, with no density accounting for cofilin subunits. The F-actin subtomogram average is then swapped for the short-repeat F-actin sub-tomogram average, showing a good match, with extra density where cofilin binds. Mesh density is coloured to match within 10 Å of the underlying atomic models.