title: Escherichia coli MutY protein has both N-glycosylase and apurinic/apyrimidinic endonuclease activities on A.C and A.G mispairs.
abstract: In Escherichia coli the mutY (or micA)-dependent DNA mismatch repair pathway can convert A degrees G and A degrees C mismatches to C.G and G.C base pairs, respectively, through a short repair-tract mechanism. The MutY protein has been purified to near homogeneity from an E. coli overproducer strain. Purified MutY has been shown to contain both N-glycosylase and 3' apurinic/apyrimidinic (AP) endonuclease activities. The N-glycosylase removes the mispaired adenines of A degrees G and A degrees C mismatches, and the AP endonuclease acts on the first phosphodiester bond 3' to the AP sites. The N-glycosylase and the nicking (combined N-glycosylase and AP endonuclease) activities copurified through multiple chromatographic steps without a change in relative specific activities. Furthermore, both N-glycosylase and AP endonuclease activities can be recovered by renaturation of a single polypeptide band from an SDS/polyacrylamide gel. Renaturation required the presence of iron and sulfide. These findings suggest that the MutY protein, like endonuclease III, is an iron-sulfur protein. DNA fragments with A degrees C mismatches were 20-fold less active than DNA with A degrees G mispairs as a substrate for purified MutY.
authors.affiliation: Department of Biological Chemistry, School of Medicine, University of Maryland, Baltimore 21201.
authors.forename: J J
authors.initials: JJ
authors.lastname: Tsai-Wu
authors.forename: H F
authors.initials: HF
authors.lastname: Liu
authors.forename: A L
authors.initials: AL
authors.lastname: Lu
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism; D045647:DNA Glycosylases; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D009699:N-Glycosyl Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D011489:Protein Denaturation; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D004706:Endodeoxyribonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase