This Domain of unknown function 61 (DUF61) family of proteins are widely distributed in archaea. In crenarchaea, the genes of DUF61 proteins are in an operon containing two genes of box C/D RNA protein complexes. The NMR structure of a DUF61 family member from the hyperthermophilic archaeon Sulfolobus solfataricus revealed a rigid core structure and flexible N- and C-terminal regions, including a negatively-charged independent C-terminal helix. The core structure consists of N- and C-terminal subdomains, in which the C-terminal subdomain shows significant structural similarity with several nucleic acid binding proteins [1].

1: Solution structure of an archaeal DUF61 family protein SSO0941 encoded by a gene\tin the operon of box C/D RNA protein complexes. Zhou T, Yao X, Wang J, Feng Y; J Struct Biol. 2018;203:179-184. PMID:29526782