] Exonuclease VII catalyses exonucleolytic cleavage in either 5' - 3' or 3'-5' direction to yield 5'-phosphomononucleotides. The large subunit also contains an N-terminal OB-fold domain that binds to nucleic acids . [ edit ] References ^ Vales LD, Rabin BA, Chase JW (August 1982). "Subunit structure of Escherichia coli exonuclease