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Molecular and General Genetics MGG

, Volume 205, Issue 1, pp 9–13 | Cite as

Structure and function ofdnaQ andmutD mutators ofEscherichia coli

  • Kyoko Takano
  • Yusaku Nakabeppu
  • Hisaji Maki
  • Takashi Horiuchi
  • Mutsuo Sekiguchi
Article

Summary

The nucleotide sequences of the recessivednaQ49 and the dominantmutD5 mutator were determined. ThednaQ49 mutator has a single base substitution in thednaQ gene, thus causing one amino acid change,96Val (GTG)→ Gly (GGG), in the DnaQ protein (ε subunit of DNA polymerase III holoenzyme). ThemutD5 mutator possesses two base substitutions in the same gene, resulting in two amino acid changes,73Leu (TTG)→Trp (TGG) and164Ala (GCA)→Val (GTA), which were designated themutD52 andmutD51 mutations, respectively. Construction of chimaeric genes carrying one or two of these mutations revealed: (1) eithermutD51 ormutD52 alone causes the dominant mutator phenotype when present in a multi-copy plasmid; (2)mutD51, but notmutD52, exerts the dominant mutator phenotype when present in a low-copy plasmid; (3) the dominantmutD51 mutator activity is suppressed by thednaQ49 mutation when both mutations are present in the same gene. Based on these findings, we devised a model for the action of these mutators.

Key words

Mutator DNA polymerase III dnaQ gene Suppression 

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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • Kyoko Takano
    • 1
  • Yusaku Nakabeppu
    • 1
  • Hisaji Maki
    • 1
  • Takashi Horiuchi
    • 1
  • Mutsuo Sekiguchi
    • 1
  1. 1.Department of Biology, Faculty of Science and Department of Biochemistry, Faculty of MedicineKyushu UniversityFukuokaJapan

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