Bifunctional Prokaryotic DNA-Methyltransferases
Restriction-modiﬁcation systems (RMS) are prokaryotic tools against invasion of foreign DNAs into cells . 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.