The subtype C restriction (R) subunit of a type I restriction enzyme that recognizes 5'-CCAN(7)RTGC-3' and cleaves a random distance away. The R subunit is required for both endonuclease and ATPase activities but not for modification. Cleaves only non-methylated DNA, hemi-methylated and fully methylated DNA are not substrates. After locating a non-methylated recognition site, the enzyme complex serves as a molecular motor that translocates DNA in an ATP-dependent manner until a collision occurs that triggers cleavage (PubMed:12654995) (By similarity). The prr locus restricts phage T4 mutants lacking polynucleotide kinase or RNA ligase; T4 mutants lacking these genes manifest a T4-induced anticodon nuclease (ACNase). This is a putative 'masking-agent' for the ACNase encoded by prrC. It is thought that Stp and other T4-encoded ACNase factors counteract the masking agents, thus activating the latent ACNase (PubMed:1691706) (Probable). Endonucleolytic cleavage of DNA to give random double-stranded fragments with terminal 5'-phosphates, ATP is simultaneously hydrolyzed. The type I restriction/modification system is composed of three polypeptides R, M and S; the restriction enzyme has stoichiometry R(2)M(2)S(1) while the methyltransferase is M(2)S(1). Manifests the latent anticodon nuclease (prrC, ACNase). Belongs to the HsdR family.