Structure of the Dimerization and β-Catenin- Binding Region of α-Catenin  Sabine Pokutta, William I. Weis  Molecular Cell  Volume 5, Issue 3, Pages 533-543 (March 2000) DOI: 10.1016/S1097-2765(00)80447-5

Figure 1 Structure of α-cat 82–279 (A) Topology diagram of the α-cat 82–279 fold. Helices are shown as cylinders and are numbered consecutively; residue numbers at the beginning and the end of the helices are indicated. The region colored in red represents the dimerization interface. (B) Ribbon diagram of α-cat 82–279 protomer structure. Two different views related by a 180° rotation about the horizontal axis are shown. Proline residues in helices 3 and 4 are shown in red. This figure, and Figures 1C, 5A, 5B, were made with MOLSCRIPT (Kraulis 1991). (C) Ribbon diagram of the α-cat 82–279 dimer. Molecular Cell 2000 5, 533-543DOI: (10.1016/S1097-2765(00)80447-5)

Figure 5 Structure-Based Sequence Alignment of α-Catenins and Related Proteins Representatives of the α-catenin family, the α-catenin-like protein, α-catulin (Janssens et al. 1999), and representatives of the vinculin family were aligned using the program CLUSTAL-W (Thompson et al. 1994). Secondary structure elements based on the βα-cat structure are indicated on the top and by the boxed areas. Hydrophobic core residues are shaded in light gray and the a and d positions of heptad repeat sequences are indicated below the alignment. Proline residues within helices are boxed. The asterisk in helix 2 denotes a switch in the heptad repeat pattern where the N-terminal part of helix 2, which packs into the four-helix bundle of the dimerization interface, turns into the C-terminal, four-helix bundle of α-cat 82–279. The sequences and their GenBank accession numbers are: mouse α(E)-catenin (117607), human α(E)-catenin (461853), Xenopus α(E)-catenin (1199644), mouse α(N)-catenin (2501658), human α(N)-catenin (117609), chicken α(N)-catenin (399311), green urchin α-catenin (1098900), Drosophila α-catenin (285752), C. elegans α-catenin (3879207), human α-catulin (3342778), mouse vinculin (3287937), human vinculin (340237), chicken vinculin (138546), C. elegans vinculin (156276). Molecular Cell 2000 5, 533-543DOI: (10.1016/S1097-2765(00)80447-5)

Figure 2 Mapping of the β-Catenin-Binding Site in α-Catenin (A) Schematic representation of α-catenin and the constructs used. N- and C-terminal ends are indicated on top. The light gray line represents the sequence visible in the α-cat 82–279 structure. (B) Interaction of GST-β-catenin with full-length α-catenin and α-catenin fragments. GST-β-catenin was incubated with full-length α-catenin or α-catenin fragments in a 1:1 or 1:5 ratio as indicated. Protein complexes were coprecipitated on glutathione agarose beads and analyzed by SDS-PAGE and Coomassie blue staining. Molecular weight markers are indicated on the left. Molecular Cell 2000 5, 533-543DOI: (10.1016/S1097-2765(00)80447-5)

Figure 3 Model of the Interaction of α- and β-Catenin Helical wheel plots of (A), the N-terminal part of the β-catenin-binding site in α-catenin, residues 57–81 and (B), the α-catenin-binding site in β-catenin, residues 120–146. a and d positions representing hydrophobic positions are labeled in red. (C) Schematic diagram of the model of the interaction of α- and β-catenin. Helices are shown as cylinders and the α-cat 82–279 structure is colored yellow. The N-terminal part of the β-catenin-binding site is shown in blue; the α-catenin-binding site in β-catenin is shown in red. Upon binding of β-catenin, the α-catenin dimer dissociates, and two helices in the four-helix bundle of the dimerization site are replaced by α helices from α- and β-catenin, respectively. Molecular Cell 2000 5, 533-543DOI: (10.1016/S1097-2765(00)80447-5)

Figure 4 Interaction of α- and β-Catenin in βα-cat (A) Superdex 75 gel filtration chromatography of α-cat 57–264 and βα-cat. Peak fractions were analyzed by SDS-PAGE and Coomassie blue staining. The estimated molecular weight for the two peaks is indicated. (B) Ribbon diagram of the chimera βα-cat. The color scheme is the same as in the schematic of the model (Figure 3). Residues 82–261, corresponding to the α-cat 82–279 protomer structure, are in yellow; residues 57–81 of α-catenin are in blue; the β-catenin sequence is in red. The flexible glycine linker between β- and α-catenin, which is not visible in the structure, is shown as a dashed green line; the N and C termini of the α-catenin and the β-catenin fragment are indicated. (C) Contacts formed by tyrosine 142. View of tyrosine 142 in the βα-cat structure. The color scheme is the same as for the βα-cat structure. Amino acids interacting with tyrosine 142 are shown in ball and stick representation. Carbon, nitrogen, and oxygen atoms are shown as gray, blue, and red spheres, respectively. α and β indicate that these amino acids belong to α-catenin and β-catenin, respectively. Nonpolar van der Waals contacts are indicated by thin lines; hydrogen bonds are shown as thin, dashed lines. Molecular Cell 2000 5, 533-543DOI: (10.1016/S1097-2765(00)80447-5)