Abstract

The rearrangement or permutation of protein substructures is an important mode of divergence. Recent work1 explored one possible underlying mechanism called permutation‐by‐duplication, which produces special forms of motif rearrangements called circular permutations. Permutation‐by‐duplication, involving gene duplication, fusion and truncation, can produce fully functional intermediate proteins1 and thus represents a feasible mechanism of protein evolution. In spite of this, circular permutations are relatively rare and we discuss possible reasons for their existence. BioEssays 28: 973–978, 2006. © 2006 Wiley Periodicals, Inc.