Figure 2. Subnanometer-resolution reconstruction of the Vt-actin interface.
(a) Reconstructions of actin alone (left) and actin decorated with Vt ΔC5 (right). Actin, light blue, Vt, orange. (b) Rigid-body docking of the Vt crystal structure. Helix 1 (H1), which was not visualized, is colored magenta. Cryo-EM density attributed to actin and and Vt by docking analysis are colored blue and transparent grey, respectively. Difference maps of GFP-E892-VtΔC5 – VtΔC5 (pink) and VtΔC5-GFP – VtΔC5 (green) are displayed as isosurfaces contoured at 15 σ. The fusion sites for GFP constructs are labeled and displayed in space-filling representation in the same color as the corresponding difference maps. Density tentatively attributed to Vt rearrangements is magenta. (c) Colored as in b, a view highlighting the density on the actin surface. Actin 1 is displayed as an electrostatic potential surface map, contoured at +/− 10 KbT/e (blue, positive; red, negative). (d) Colored as in b, a view of the Vt H4-H5 helical hairpin, which fits the density poorly. Asterisk highlights a clash with the actin surface.