This domain, found in various hypothetical archaeal proteins, has no known function. However, this family was identified as belonging to the nucleotidyltransferase superfamily [1].

1: Comprehensive classification of nucleotidyltransferase fold proteins: identification of novel families and their representatives in human. Kuchta K, Knizewski L, Wyrwicz LS, Rychlewski L, Ginalski K; Nucleic Acids Res. 2009; [Epub ahead of print] PMID:19833706