What is the methyl donor of DNA (cytosine-5)-methyltransferases?
['The product of the dcm gene is the only DNA cytosine-C5 methyltransferase of Escherichia coli K-12; it catalyses transfer of a methyl group from S-adenosyl methionine (SAM) to the C-5 position of the inner cytosine residue of the cognate sequence CCA/TGG. ', 'Deoxycytosine methylase (Dcm) enzyme activity causes mutagenesis in vitro either directly by enzyme-induced deamination of cytosine to uracil in the absence of the methyl donor, S-adenosylmethionine (SAM), or indirectly through spontaneous deamination of [5-methyl]cytosine to thymine', 'In the absence of DNA substrate, the DNA methyltransferase (MTase) M.BspRI can methylate itself using the methyl donor S-adenosyl-L-methionine (AdoMet). The methyl group is transferred to two Cys residues of the MTase.', 'The reaction is fairly insensitive to the methyl donor in the reaction, S-adenosylmethionine.', 'Formation of the complex was dependent upon the presence of the methyl donor S-adenosylmethionine, suggesting that it comprises an enzyme-linked 5-substituted dihydrocytosine moiety in DNA. ', 'The DNA (cytosine-5)-methyltransferase (m5C-MTase) M.BspRI is able to accept the methyl group from the methyl donor S-adenosyl-L-methionine (AdoMet) in the absence of DNA. Transfer of the methyl group to the enzyme is a slow reaction relative to DNA methylation. S', 'Here, we report the structure of HhaI methyltransferase in complex with DNA containing a south-constrained abasic carbocyclic sugar at the target site in the presence of the methyl donor byproduct AdoHcy.']
['S-adenosyl-L-methionine (AdoMet, SAM) is the methyl donor of DNA (cytosine-5)-methyltransferases. DNA (cytosine-5)-methyltransferases catalyze the transfer of a methyl group from S-adenosyl-L-methionine to the C-5 position of cytosine residues in DNA.']
['S-adenosyl-L-methionine']