This superfamily represents the bacterial antirestriction (ArdA) protein C-terminal domain 3. ArdA functions in bacterial conjugation to allow an unmodified plasmid to evade restriction in the recipient bacterium and yet acquire cognate modification PMID:12618468. ArdA forms a dimer and each monomer is comprised of three small alpha-beta domains, each with a different fold, arranged in a row in each monomer.

This entry represents domain 3 located at the C-terminal end of the monomeric subunit of ArdA. The C-terminal domain has a three-stranded beta-sheet and three alpha-helices packed together in a manner that creates a groove in the structure. The helical arrangement in the C-terminal domain contains a component of the winged helix-turn-helix motif. The evolution of ArdA is curious as domains 2 and 3 show a similar fold to that of nucleotide binding proteins but the opposite charge to the characteristic positive charge of oligonucleotide binding proteins. This reversal in surface potential suggests that ArdA is not a DNA- (or RNA)-binding protein PMID:19506028.

PFAM:PF07275,INTERPRO:IPR009899