A family of uncharacterised proteins found by clustering human gut metagenomic sequences [1]. This domain is likely to be related to the Toprim domain.

1: Expansion of the protein repertoire in newly explored environments: human gut microbiome specific protein families Ellrott K, Jaroszewski L, Weizhong L, Wooley J, Godzik, A PLoS Computational Biology, 2010 PMID:20532204