EXONUCLEASE-IX OF ESCHERICHIA-COLI REMOVES 3'-PHOSPHOGLYCOLATE END-GROUPS FROM DNA

The bacteria Escherichia coli contains several exonucleases acting on both double- and single-stranded DNA, and in both a 5' --> 3' and a 3' --> 5' direction. These enzymes are involved in replicative, repair a nd recombination functions. A new exonuclease recently identified in E . coli, termed exonuclease IX, acts preferentially on single-stranded DNA as a 3' --> 5' exonuclease and also functions as a 3' phosphodiest erase on DNA containing 3' incised apurinic/apyrimidinic (AP) sites to remove the product trans-4-hydroxy-2-pentenal-5-phosphate. We now dem onstrate that the enzyme is also able to remove 3' phosphoglycolate en d groups from DNA. This activity may have an important role in DNA bas e excision repair in E. coli. (C) 1998 by Radiation Research Society.