Escherichia coli single-stranded DNA binding protein stimulates the DNA deoxyribophosphodiesterase activity of exonuclease I

Abstract

The E.coil single-stranded binding protein (SSB) has been demonstrated In vitro to be involved in a number of replicatlve, DNA renaturatlon, and protective functions. It was shown previously that SSB can interact with exonuclease I to stimulate the hydrolysis of single-stranded DNA. We demonstrate here that E.coil SSB can also enhance the DNA deoxyrlbo-phosphodiesterase (dRpase) activity of exonuclease I by stimulating the release of 2-deoxyrlbose-5-phos-phate from a DNA substrate containing AP endo-nuclease-inclsed AP sites, and the release of 4-hydroxy-2-pentenal-5-phosphate from a DNA substrate containing AP lyase-incised AP sites. E.coil SSB and exonuclease I form a protein complex as demonstrated by Superose 12 gel filtration chromato-graphy. These results suggest that SSB may have an important role in the DNA base excision repair pathway. © 1994 Oxford University Press.