Journal of Molecular Evolution

, Volume 49, Issue 1, pp 161–164 | Cite as

Circular Permutations in the Molecular Evolution of DNA Methyltransferases

  • Albert  Jeltsch


Circular permutations of genes during molecular evolution often are regarded as elusive, although a simple model can explain these rearrangements. The model assumes that first a gene duplication of the precursor gene occurs in such a way that both genes become fused in frame, leading to a tandem protein. After generation of a new start codon within the 5′ part of the tandem gene and a stop at an equivalent position in the 3′ part of the gene, a protein is encoded that represents a perfect circular permutation of the precursor gene product. The model is illustrated here by the molecular evolution of adenine-N6 DNA methyltransferases. β- and γ-type enzymes of this family can be interconverted by a single circular permutation event. Interestingly, tandem proteins, proposed as evolutionary intermediates during circular permutation, can be directly observed in the case of adenine methyltransferases, because some enzymes belonging to type IIS, like the FokI methyltransferase, are built up by two fused enzymes, both of which are active independently of each other. The mechanism for circular permutation illustrated here is very easy and applicable to every protein. Thus, circular permutation can be regarded as a normal process in molecular evolution and a changed order of conserved amino acid motifs should not be interpreted to argue against divergent evolution.

Key words: Amino acid sequence motif — Divergent evolution — DNA methyltransferase — Gene duplication — Protein evolution — Restriction/modification system — Tandem enzyme 


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Copyright information

© Springer-Verlag New York Inc. 1999

Authors and Affiliations

  • Albert  Jeltsch
    • 1
  1. 1.Institut für Biochemie, Fachbereich Biologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, GermanyDE

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