Methyltransferases -- Congresses : Biochemistry of S-adenosylmethionine and related compounds : proceedings of a conference held at the Lake of the Ozarks (Missouri) on October 26-29, 1981 / organized by Earl Usdin, Ronald T Borchardt, Cyrus R Creveling
Enzymes that are part of the restriction-modification systems. They are responsible for producing a species-characteristic methylation pattern, on either adenine or cytosine residues, in a specific short base sequence in the host cell's own DNA. This methylated sequence will occur many times in the host-cell DNA and remain intact for the lifetime of the cell. Any DNA from another species which gains entry into a living cell and lacks the characteristic methylation pattern will be recognized by the restriction endonucleases of similar specificity and destroyed by cleavage. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms
