DNA methyltransferases are a prolific example of how different topologies might relate through circular permutation.

Circular permutation of a protein consists of connecting the native N- and C-termini covalently with a peptide linker and cleaving the peptide backbone at one specific site 3.

Roney Graf, H. K. Schachman, Random Circular Permutation of Genes and Expressed Polypeptide Chains: Application of the Method to the Catalytic Chains of Aspartate Transcarbamoylase, Proceedings of the ...