Evolutionary scenario for the origin of three folds from an ancestral helix-strand-helix motif. The coloring and representative proteins are as in Fig. 2. The superimposed ensemble of helix-strand-helix motifs consists of motifs from the following proteins: yellow (1IN4: residues 181–212; 1B67: 4–33), green (1IN4: 216–251; 1B67: 134–166; 1K6K: 82–115).
Alva et al. BMC Structural Biology 2007 7:17 doi:10.1186/1472-6807-7-17