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Bifunctional Prokaryotic DNA-Methyltransferases
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Restriction-modification systems (RMS) are prokaryotic tools against invasion of foreign DNAs into cells [1]. They reduce horizontal gene transfer, thus stimulating microbial biodiversity. Usually, they consist of a restriction endonuclease (REase) and a modification DNA methyltransferase (MTase) enzyme recognising the same short 4-8 nucleotide sequence. MTase is responsible for methyl group transfer to adenine or cytosine nucleotides within the target sequence, thus preventing its hydrolysis by cognate REase.