This domain is found at the C-terminal end of PT26-6P, a large protein encoded by a plasmid from the hyperthermophilic archaea Thermococcus. This protein, present in all members of a family of mobile elements, has homologues in archaeal genomes. This entry represents the third and final domain, which folds as a five-helical bundle that contains five antiparallel helices [1]. Its function is unknown.

1: A protein encoded by a new family of mobile elements from Euryarchaea exhibits three domains with novel folds. Keller J, Leulliot N, Soler N, Collinet B, Vincentelli R, Forterre P, van Tilbeurgh H; Protein Sci. 2009;18:850-855. PMID:19319959