The middle section of a putative type I restriction enzyme that if reconstituted might recognize 5'-GAN(7)TAY-3' and cleave a random distance away (Probable). Subunit R is required for both nuclease and ATPase activities, but not for modification (PubMed:12654995). Could be the product of a pseudogene; in this organism the endonuclease subunit carries 2 frameshift mutations (resulting in 3 short ORFs) and is probably not expressed.