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skos:definition |
MSH: 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.,NCI: DNA Methyltransferases are a subclass of transferase enzymes that catalyze the transfer of a methyl group from a donor compound to DNA.,NCI: An enzyme (a protein that speeds up chemical reactions in the body) that attaches a methyl group to DNA. A methyl group is a chemical group containing one carbon and three hydrogen molecules.
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