Fig. 1.

Comparison of emergent and conserved architecture evolutionary models (using the threefold symmetric β-trefoil fold as example) [23, 24]. A fundamental difference between these models is the ability of simple peptide motifs to achieve complex (symmetric) architecture (via oligomerization) in the conserved architecture model. Coloring is used to indicate individual polypeptide chains. The relative order of the repeated domains A, A’, and A” is potentially variable and dependent upon the particular mechanism of duplication [18]