Figure 4. Major ABD conformational rearrangements upon actin binding.

(A) Cartoons and crystal structures of pre-bound (meta)vinculin ABD (PDB 1st6, dark orange, top) and α-catenin ABD (PDB 4igg chain B, dark pink, bottom). Regions that undergo major rearrangements are highlighted in brown (metavinculin) or magenta (α-catenin); regions not resolved in the actin-bound cryo-EM structures are transparent. (B) Cryo-EM structures of metavinculin ABD (orange, top) and α-catenin ABD (pink, bottom). Flexible regions colored as in (A); actin, shades of blue. (C) Superimposed pre-bound and post-bound structures of metavinculin ABD (top) and α-catenin ABD (bottom). Green arrows indicate displacement of helices; rotation angles indicate repositioning of C-terminal extensions (CTEs).

Figure 4—figure supplement 1. (Meta)vinculin and α-catenin activation mechanisms.

(A and B) Superimposed pre-bound full-length vinculin crystal structure (PDB 1st6) and post-bound metavinculin ABD cryo-EM structure in the absence of actin (A), or in the presence of actin (B). (C, D, E, and F) Superimposed pre-bound full-length α-catenin crystal structures (PDB 4igg: C and D: Chain B; E and F: Chain A) and post-bound α-catenin ABD cryo-EM structure without (C and E) or with (D and F) actin. (G) Superimposed pre-bound full-length vinculin crystal structure (PDB 1st6) and post-bound α-catenin ABD cryo-EM structure in the presence of actin highlights the similar orientations of their CTEs.

Figure 4—video 1. Overall conformational changes in ABDs upon actin binding.

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Linear interpolation morph of pre-bound to post-bound structures of the (meta)vinculin ABD (left) and α-catenin ABD (right). Colors, views, and superpositions are equivalent to Figure 4A and B.

Figure 4—video 2. Rearrangements in the helical bundle regions of ABDs upon actin binding.

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Linear interpolation morph of pre-bound to post-bound structures of the (meta)vinculin ABD (left) and α-catenin ABD (right), focused on their similar twisting re-arrangements in helices H2–H5. Colors, views, and superpositions are equivalent to Figure 4C.