The structure of the DUF520 family of uncharacterised proteins shows that it has composed of two domains each of which has the same topology [1].

1: Crystal structure of the YajQ protein from Haemophilus influenzae reveals a tandem of RNP-like domains. Teplyakov A, Obmolova G, Bir N, Reddy P, Howard AJ, Gilliland GL; J Struct Funct Genomics. 2003;4:1-9. PMID:12943362