 The similarity in the catalytic domains of C5-cytosine methyltransferases and N6 and N4-adenine methyltransferases provided great interest in understanding the basis for functional similarities and dissimilarities.The methyltransferases or methylases are classified into three groups (Groups α, β, and γ) based on the sequential order of certain 9 motifs and the Target Recognition Domain (TRD).Motif I consists of a Gly-X-Gly tripeptide and is referred to as the G-loop and is implicated in the binding of the S-Adenosyl methionine cofactor.