This family includes the SinI (recognises and cleaves G^GWCC) restriction endonuclease.

1: Horizontal gene transfer contributes to the wide distribution and evolution of type II restriction-modification systems. Jeltsch A, Pingoud A; J Mol Evol. 1996;42:91-96. PMID:8919860

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