Homogeneous Escherichia coli FPG protein. A DNA glycosylase which excises imidazole ring-opened purines and nicks DNA at apurinic/apyrimidinic sites.
The repair of 2,6-diamino-4-hydroxy-5-N-methyl-formamidopyrimidine (Fapy) residues in DNA is performed by a Fapy-DNA glycosylase activity which is encoded for by the fpg gene in Escherichia coli. Besides DNA glycosylase activity, this protein, the FPG protein, is endowed with an EDTA-resistant activity nicking DNA at apurinic/apyrimidinic (AP) sites. To overproduce the FPG protein, the fpg gene was placed under the control of the tac promoter in the expression vector pKK223-3 yielding the pFPG230 plasmid. The production of the FPG protein in cells harboring the pFPG230 plasmid was 800-fold higher than that of the wild type strain after induction by isopropyl-beta-D-thio-galactopyranoside. From these cells, the FPG protein was purified to homogeneity in sufficient quantity to study its physical and catalytic properties. In its active form, the FPG protein is a globular monomer of 31 kDa and has an experimentally measured isoelectric point of 8.5. When the FPG protein is heat-denatured in the presence of EDTA the two activities are more rapidly inactivated than when heated in the absence of EDTA, suggesting that the FPG protein possesses a tightly bound metal ion. Atomic absorption spectrophotometric analysis shows that there is one zinc/FPG protein molecule. The FPG protein is different from previously described DNA glycosylases and AP-nicking enzymes in E. coli. The contribution of the AP-nicking activity associated with the FPG protein represents 10-20% of the total EDTA-resistant AP-nicking activities in E. coli.
Boiteux
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S
UA147 Centre National de la Recherche Scientifique, Institut Gustave Roussy, Villejuif, France.
O'Connor
T R
TR
Lederer
F
F
Gouyette
A
A
Laval
J
J
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043382:DNA-Formamidopyrimidine Glycosylase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D013379:Substrate Specificity
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase