Members of this family of prokaryotic restriction endonucleases recognise the palindromic tetranucleotide sequence 5'-CCGG and cleave between the first and second nucleotides, leaving 2 base 5' overhangs. They fold into an alpha/beta architecture, with a five-stranded mixed beta-sheet sandwiched on both sides by alpha-helices [1].

1: An asymmetric complex of restriction endonuclease MspI on its palindromic DNA recognition site. Xu QS, Kucera RB, Roberts RJ, Guo HC; Structure. 2004;12:1741-1747. PMID:15341737

2: Sequence, structure and functional diversity of PD-(D/E)XK phosphodiesterase superfamily. Steczkiewicz K, Muszewska A, Knizewski L, Rychlewski L, Ginalski K; Nucleic Acids Res. 2012;40:7016-7045. PMID:22638584