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Volume 1

Full article

Comparison of protein structures reveals monophyletic origin of AdoMet-dependent methyltransferase family and mechanistic convergence rather than recent differentiation of N4-cytosine and N6-adenine DNA methylation

Janusz M. Bujnicki

Molecular Biology Research Program, Henry Ford Health System, One Ford Place, Suite 5D, Detroit, MI 48202, USA
E-mail: iamb@ibbrain.ibb.waw.pl or jbujnic1@hfhs.org


Edited by N. A. Kolchanov; received February 19, 1999; revised May 19, 1999; accepted June 15, 1999

Abstract

Phylogenetic analysis of the S-adenosyl-L-methionine-dependent methyltransferases was performed based on similarity of positions of main chain a-carbon atoms in published structures of members of this superfamily. The evolutionary tree was inferred and the problem of mono/polyphyletic origin of DNA methyltransferases from the Rossmann-fold enzymes was solved, bridging two seemingly antithetical hypotheses. The comparison of protein structures provides evidence for an evolutionary link between widely diverged subfamilies of RNA and DNA N6-adenine methyltransferases and argues against the close homology of N6-adenine and N4-cytosine methyltransferases, apparent from biochemical data and comparison of fragments of sequences. Such evolutionary analysis of methyltransferases has never been published yet in the literature and will guide further phylogenetical studies based on both sequence and structure comparison.

Key words: AdoMet-dependent methyltransferases, dehydrogenases, Rossmann-fold proteins, structure comparison, divergent evolution, molecular phylogenetics