title: Purification and cloning of Micrococcus luteus ultraviolet endonuclease, an N-glycosylase/abasic lyase that proceeds via an imino enzyme-DNA intermediate.
abstract: Although Micrococcus luteus UV endonuclease has been reported to be an 18-kDa enzyme with possible homology to the 16-kDa endonuclease V from bacteriophage T4 (Gordon, L. K., and Haseltine, W. A. (1980) J. Biol. Chem. 255, 12047-12050; Grafstrom, R. H., Park, L., and Grossman, L. (1982) J. Biol. Chem. 257, 13465-13474), this study describes three independent purification schemes in which M. luteus UV damage-specific or pyrimidine dimer-specific nicking activity was associated with two proteins of apparent molecular masses of 31 and 32 kDa. An 18-kDa contaminant copurified with the doublet through many of the chromatographic steps, but it was determined to be a homolog of Escherichia coli ribosomal protein L6. Edman degradation analyses of the active proteins yielded identical NH2-terminal amino acid sequences. The corresponding gene (pdg, pyrimidine dimer glycosylase) was cloned. The protein bears strong sequence similarities to the E. coli repair proteins endonuclease III and MutY. Nonetheless, traditionally purified M. luteus protein acted exclusively on cis-syn thymine dimers; it was unable to cleave site-specific oligonucleotide substrates containing a trans-syn -I, (6-4), or Dewar thymine dimer, a 5,6-dihydrouracil lesion, or an A:G or A:C mismatch. The UV endonuclease incised cis-syn dimer-containing DNA in a dose-dependent manner and exhibited linear kinetics within that dose range. Enzyme activity was inhibited by the presence of NaCN or NaBH4 with NaBH4 additionally being able to trap a covalent enzyme-substrate product. These last findings confirm that the catalytic mechanism of M. luteus UV endonuclease, like those of other glycosylase/AP lyases, involves an imino intermediate.
authors.affiliation: Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston 77555-1071, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Piersen
authors.forename: M A
authors.initials: MA
authors.lastname: Prince
authors.forename: M L
authors.initials: ML
authors.lastname: Augustine
authors.forename: M L
authors.initials: ML
authors.lastname: Dodson
authors.forename: R S
authors.initials: RS
authors.lastname: Lloyd
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004249:DNA Damage; D045647:DNA Glycosylases; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007097:Imines / Q000378:metabolism; D016982:Micrococcus luteus / Q000201:enzymology* / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D007097:Imines; D009097:Multienzyme Complexes; D012269:Ribosomal Proteins; C031249:ribosomal protein L6; C032219:UV endonuclease; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase