Circular permutation (CP) of a protein can be visualized as if its original termini were linked and new ones created elsewhere. Since the first observation of CP in plant lectins, a substantial number of natural examples have been reported, including -glucanases, swaposins, glucosyltransferases, -glucosidases, SLH domains, transaldolases, C2 domains, FMN-binding proteins, double- -barrels, glutathione synthetases, methyltransferases, ferredoxins, and proteinase inhibitors. In most of the cases, circular permutants (CPs) have conserved function or enzymatic activity, sometimes with increased functional diversity.