A family of uncharacterized proteins found by clustering human gut metagenomic sequences [1]. This domain is found associated with an Pfam:PF07275 like domain. This suggests that this family may also be involved in evading host restriction.

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