Domain 5 is found in dimeric beta-D-galactosidase from Paracoccus sp. 32d, which contributes to stabilization of the functional dimer. It is suggested that the location of this domain 5, may be one of the factors responsible for the creation of a functional dimer and cold-adaptation of this enzyme [1].

1: Structural studies of a cold-adapted dimeric beta-D-galactosidase from Paracoccus sp. 32d. Rutkiewicz-Krotewicz M, Pietrzyk-Brzezinska AJ, Sekula B, Cieslinski H, Wierzbicka-Wos A, Kur J, Bujacz A; Acta Crystallogr D Struct Biol. 2016;72:1049-1061. PMID:27599737