This antiparallel beta sandwich domain occurs in mollusc haemocyanins. Each mollusc haemocyanin contains several globular oxygen binding functional units. Each unit consists of an alpha-helical copper binding domain (Pfam:PF00264) and an antiparallel beta sandwich domain [1-2].

1: The structure of a functional unit from the wall of a gastropod hemocyanin offers a possible mechanism for cooperativity. Perbandt M, Guthohrlein EW, Rypniewski W, Idakieva K, Stoeva S, Voelter W, Genov N, Betzel C; Biochemistry. 2003;42:6341-6346. PMID:12767214

2: Crystal structure of a functional unit from Octopus hemocyanin. Cuff ME, Miller KI, van Holde KE, Hendrickson WA; J Mol Biol. 1998;278:855-870. PMID:9614947