The methylase domain (IPR002052) is often found next to the Restriction endonuclease type I HsdR N-terminal (IPR007409) domain in restriction endonucleases or methylases. The R subunit (HsdR) of type I enzymes contains the N-terminal domain. The representative type I enzyme is EcoKI, which recognizes the DNA sequence 5'-AACN6GTGC-3'. The R protein (HsdR) is necessary for nuclease and ATPase activities. The Type I enzyme functions by requiring ATP and S-adenosyl-L-methionine, cleaves at a location distant from the recognition site, and is a multifunctional protein that also performs methylase and restriction functions. The prokaryotic DNA restriction modification machinery, which keeps organisms safe from foreign DNA invasion, depends on type I restriction endonucleases.