Duplication, divergence and formation of novel protein topologies

The rearrangement or permutation of protein substruc-tures is an important mode of divergence. Recent work(1) explored one possible underlying mechanism called permutation-by-duplication, which produces special forms of motif rearrangements called circular permu-tations. Permutation-by-duplication, involving gene duplication, fusion and truncation, can produce fully functional intermediate proteins(1) 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. Permutations are one form of protein divergence Since the first protein structures and sequences becam