Sequence motifs characteristic for DNA [cytosine-N4] and DNA [adenine-N6] methyltransferases. Classification of all DNA methyltransferases.

Two additional conserved motifs (CM), CM Is and CM III, have been found in addition to well-known CM I and CM II within the primary amino acid sequences of almost all m6A- and m4C-methyltransferases (MTases). The boundaries of all four CM were defined and their consensus sequences characteristic both for different classes, as well as for all N-MTases, were derived. Some regular deviations at fixed positions of the consensus sequences CM Is, CM I and CM II, typical for separate classes of N-MTases, were presumed to correlate. A possible structural basis for the supposed interregional correlations is discussed and experiments for verification of the assumed interactions between CM are suggested. A classification scheme for all N-MTases is provided.