This domain consists of 4 beta strands and two alpha helices which make up the dimerisation surface of members of the M20 family of peptidases [1]. This family includes a range of zinc metallopeptidases belonging to several families in the peptidase classification [2]. Family M20 are Glutamate carboxypeptidases. Peptidase family M25 contains X-His dipeptidases.

1: Crystal structure of carboxypeptidase G2, a bacterial enzyme with applications in cancer therapy. Rowsell S, Pauptit RA, Tucker AD, Melton RG, Blow DM, Brick P; Structure 1997;5:337-347. PMID:9083113

2: Evolutionary families of metallopeptidases. Rawlings ND, Barrett AJ; Meth Enzymol 1995;248:183-228. PMID:7674922