Exonuclease VII

The enzyme exodeoxyribonuclease VII is a bacterial exonuclease enzyme. It is composed of two nonidentical subunits; one large subunit and 4 small ones. that catalyses exonucleolytic cleavage in either 5′- to 3′- or 3′- to 5′-direction to yield nucleoside 5′-phosphates. The large subunit also contains an N-terminal OB-fold domain that binds to nucleic acids.
The widely used quinolone antibiotics induce DNA damage in bacterial cells by trapping DNA gyrase, leading to blocked gyrase cleavage complexes. Exonuclease VII participates in repairing such DNA damage by resolving the trapped cleavage complexes.
When Escherichia coli bacteria recA mutants are UV-irradiated, “reckless” DNA degradation occurs that involves exonuclease VII.