This domain [1] is the short zinc-binding loops region of a number of much longer chain homing endonucleases. Such loops are probably stabilised by the zinc and may be viewed as small but separate domains. The common structural feature of these domains is that at least three zinc ligands lie very close to each other in the sequence and are not incorporated into regular secondary structural elements. The biological roles played by these small zinc-binding domains are presently unknown [2].

1: A novel endonuclease mechanism directly visualized for I-PpoI. Galburt EA, Chevalier B, Tang W, Jurica MS, Flick KE, Monnat RJ Jr, Stoddard BL; Nat Struct Biol. 1999;6:1096-1099. PMID:10581547

2: Structural classification of zinc fingers: survey and summary. Krishna SS, Majumdar I, Grishin NV; Nucleic Acids Res. 2003;31:532-550. PMID:12527760