Exonuclease III

Catalyzes the stepwise removal of mononucleotides from 3´-hydroxyl termini of duplex DNA. A limited number of nucleotides are removed during each binding event, resulting in coordinated progressive deletions within the population of DNA molecules. Exonuclease III has also been reported to have RNase H, 3´-phosphatase and AP-endonuclease activities. The preferred substrates are blunt or recessed 3´-termini, although the enzyme also acts at nicks in duplex DNA to produce single-strand gaps. 3´-protruding termini are resistant to cleavage; the degree of resistance depends on the length of the extension,with extensions 4 bases or longer being essentially resistant to cleavage. Exonuclease III is produced by recombinant expression in E. coil.