A P subtype restriction enzyme that recognizes the double-stranded sequence 5'-CCN(7)GG-3' and cleaves after N-7. Endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates. Binds 2 Zn(2+) ions per subunit. Is one of the thermostable restriction enzymes that remain active after 20 to 30 cycles of thermal PCR cycling. Heterotetramer of two alpha and two beta subunits. The alpha subunit is believed to be responsible for DNA recognition, while the beta subunit is thought to mediate cleavage. One of the zinc-binding motifs may participate in protein-DNA interactions and the other might mediate protein-protein interactions. Could be used to screen carcinogenic mutations in a restriction endonuclease-mediated selective PCR (or REMS-PCR) assay. In particular, could be used to detect the vast majority of mutations that occur at codons 12 or 13 of the Ras oncogenes that encode glycine (codons GGN) at those positions.