Fig. 4: Actin nucleotide state modulates subunit shearing during filament bending.
From: Bending forces and nucleotide state jointly regulate F-actin structure
a, Cryo-EM maps of bent ADP–F-actin (blue) and ADP-Pi–F-actin (orange), coloured by strand. Protomer numbering is indicated. The dashed and solid lines represent the convex and concave sides of the bent filament, respectively. b, Ribbon representation of an individual actin protomer coloured by subdomain (left). The spheres connected by bars indicate subdomain centroids. Right, protomer subdomain centroid diagrams with vectors (scaled 100×), indicating subdomain-averaged displacements from the corresponding helically symmetric model. c, Plots of subdomain shear indices (representing coordinated rearrangements) of subdomains 1 and 4 (top) and subdomains 2 and 3 (bottom). Blue lines, ADP; orange lines, ADP-Pi. The solid and dashed lines represent even (concave side) and odd (convex side) protomers, respectively. AU, arbitrary units. d, Cα representation of the indicated protomers’ nucleotide clefts from bent ADP–F-actin and ADP-Pi–F-actin, coloured by per-residue strain pseudoenergy. ADP (dark green), magnesium (light green) and phosphate (orange) are shown in stick representation. e, Quantification of each protomer’s nucleotide cleft strain pseudoenergy, compared between nucleotide states and bending conditions (top). Bottom, equivalent quantification of solvent-accessible volume of nucleotide clefts. Data are mean ± 95% confidence interval. n = 7 (bent) and n = 14 (straight). Statistical comparison was performed using one-way analysis of variance with Tukey post hoc analysis; P values were corrected for multiple comparisons. f, Cartoon model of the steric boundary mechanism for joint regulation of F-actin by bending forces and nucleotide state.
