JBC, Vol. 253, Issue 9, 2990-2999, May, 1978
A DNase for apurinic/apyrimidinic sites associated with exonuclease III of Hemophilus influenzae
J. E. Clements, S. G. Rogers and B. Weiss
An endonuclease purified from Hemophilus influenzae made single strand
breaks in DNA containing apurinic or apyrimidinic sites but had no
detectable endonuclease activity on untreated native DNA. The new
5'-termini created at the cleavage sites were base-free deoxyribose
5-phosphate residues. The enzyme preparation also catalyzed the
exonucleolytic release of 5'-mononucleotides from bihelical DNA and the
hydrolysis of DNA 3'-terminal phosphomonoesters. The
phosphatase-exonuclease activity was indistinguishable from that reported
by Gunther and Goodgal (J. Biol. Chem. (1970) 245, 5341-5349) and resembled
that of exonuclease III of Escherichia coli. The endonucleolytic and
exonucleolytic activities could not be separated by electrophoresis,
sedimentation, or gel filtration, and they were also affected
simultaneously by mutation. The enzymatic activities appear to be functions
of a single monomeric protein (M(r) = 30,000).