An Adenosine Triphosphate-dependent Deoxyribonuclease from Hemophilus influenzae Rd

The ATP-dependent DNase from Hemophilus influenzae has an unusual substrate specificity. The enzyme attacks linear duplex DNA to give initial products which are several hundred base pairs in length, suggesting an endonucleolytic mechanism. However, the enzyme differs from many other endonucleases in that it will not attack either single or double strand circular DNA, or duplex circles with nicks or gaps. These findings suggest that the enzyme requires a substrate with a free end. This requirement may be topological, as various enzymatic modifications of the termini do not affect the activity of the enzyme.