Putative catalytic domain of type II restriction enzyme NgoFVII and similar proteins
Putative catalytic domain of type II restriction enzyme NgoFVII (EC 3.1.21.4), which shows high sequence similarity to type IIs restriction endonuclease BfiI. Type II restriction endonucleases are components of restriction modification (RM) systems that protect bacteria and archaea against invading foreign DNA. They usually function as homodimers or homotetramers that cleave DNA at defined sites of 4 to 8 bp in length, and they require Mg2+, not ATP or GTP, for catalysis. The prototype of this subfamily is the NgoFVII restriction endonuclease from Neisseria gonorrhoeae. It plays an essential role in the endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates. It recognizes the double-stranded sequence GCSGC and cleaves after G-4. Members of this subfamily contain one copy of the conserved HKD motif (H-x-K-x(4)-D, where x represents any amino acid residue) per protein chain and have been classified into the phospholipase D (PLD, EC 3.1.4.4) superfamily.
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