Structural domains comprising this superfamily share the structure of domain 2 of the antirestriction protein ArdA. This protein is found in prokaryotes, including important pathogenic species, and enables associated mobile genetic elements to evade the ubiquitous Type I DNA restriction systems thus assisting the spread of resistance genes in bacterial populations. ArdA forms a dimer and each monomer is comprised of three small domains arranged in a row in each monomer. Domains 2 and 3 have folds similar to those of nucleotide binding proteins, but which present a negative potential, opposite to the positive potential characteristic of nucleotide binding proteins. This reversal in surface potential suggests that ArdA is not a DNA- (or RNA)-binding protein PMID:19506028.

PFAM:PF07275,INTERPRO:IPR009899